Added, Visual mode: added "Toggle Alpha-based Texture Highlighting" action. When enabled, 3d floor textures and middle textures on double-sided lines will be highlighted only when the crosshair points at a non-transparent pixel.
Changed: multi-part sectors are now better preserved after drawing new lines.
Changed, TEXTURES parser: patch loading errors are now ignored for textures with "NullTexture" option.
Changed, Game configurations: changed default door action arguments to better match vanilla ones.
Fixed, Actions: in some cases keyboard shortcuts involving Ctrl/Alt/Shift modifier keys were displayed incorrectly.
Fixed(?): probably fixed inability to save map wad in Slade 3.
Updated ZDoom_ACS.cfg.
Updated ZDoom_DECORATE.cfg.
Updated ZDoom ACC.

Added, Find and Replace mode: you can now search (and replace) unset sidedef/linedef/thing/sector flags.
Changed, TEXTURES parser: patch loading errors are now treated as warnings for optional textures.
Changed, TEXTURES parser: patch loading is now skipped for textures with "NullTexture" option.

Added Preferences -> Editing -> "Switch view modes when switching to the same Classic Mode" option (disabled by default). When enabled, view mode will be switched between "view floor textures" and "view ceiling textures" when activating the same 2D mode repeatedly.

Changed, Classic modes: displayed mouse map position coordinates are now snapped to current grid size.
Updated model pitch handling to match current GZDoom implementation.
Fixed imprecise vertex coordinates generated by Draw Ellipse mode.
Fixed a resource loading exception when opened map file wad was located in the root of a Directory resource.
Internal: changed output of all InterpolationTools methods from int to float.
Fixed, Internal: InterpolationTools.InterpolateColor() delta usage was inverted.

Added 3 map geometry dragging modes (used when applying Drag Vertices/Linedefs/Sectors modes and Edit Selection mode):
- "Merge Dragged Vertices Only". Only vertex-line intersections will be processed (DB2 mode).
- "Merge Dragged Geometry". Geometry merging will be performed.
- "Replace with Dragged Geometry". Dragged geometry will replace underlaying geometry.
You can switch between these using 3 new actions, top toolbar buttons and Edit menu buttons.
Changed: activating the same 2D mode repeatedly now toggles View modes.
Renamed "Merge Geometry" action/menu item to "Snap to Geometry".
More fixes to vertex/linedef/sector dragging logic.
Updated ZDoom_DECORATE.cfg.

Rewritten vertex/linedef/sector dragging logic. Now it processes line-line intersections. And handles more corner cases. And has less bugs. Probably.
Fixed, Edit Selection mode: texture scale was flipped when "Floor/Ceiling Transform" -> "Scale" was enabled.
Changed: a warning is no longer displayed when trying to compile an empty SCRIPTS lump.
Updated ZDoom_DECORATE.cfg.

Fixed, Drag Linedefs, Drag Vertices, Edit Selection modes: in some cases sidedefs were incorrectly removed when modifying a closed section of a multi-part sector.
Fixed, Drag Linedefs, Drag Vertices, Drag Sectors, Edit Selection modes: in some cases sidedef textures were not adjusted after applying the modes, leaving middle textures on double-sided lines.

Added, Edit Selection mode: Added "Adjust height" setting. It can be used to adjust floor/ceiling height of selected sectors based on the sector selection was in and the sector selection was moved into.
Removed "Adjust heights to match relatively with surrounding sector" option from Preferences -> Pasting, because sector height adjustments are now handled by Edit Selection mode.
Fixed, Sector info panel: in some cases 0 deg. floor/ceiling texture rotation was triggering texture offset/scale/rotation UI parts to be shown.
Fixed even more cases when sidedefs belonging to linedefs, which were moved on top of existing linedefs, were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.
Fixed, Bridge mode: in some cases calculated floor/ceiling heights were not applied to the sectors created by the mode.
Changed, internal: changed program's CurrentCulture to InvariantCulture.

Changed, internal: made TextLabel and IRenderer2D public properties compatible with DB2 implementation.
Fixed some more cases when sidedefs belonging to linedefs, which were moved on top of existing linedefs, were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.
Fixed, Map Analysis mode: error checks must be updated after switching map format.

Added "safeboundary" game configuration property. The value determines the maximum map bounding box size considered to be safe by "Check map size" error check.
Changed, Map Analysis mode: some checks are now available only under certain conditions (for example, "Check polyobjects" is now available only when the map is in Hexen or UDMF map format).
Updated documentation ("Game Configuration - Basic Settings" page).

Added: sectors are now split into multiple sectors when their shape is divided into several closed shapes by drawing new geometry or dragging existing geometry using Edit Selection and Drag Geometry modes.
Fixed: in some cases sidedefs belonging to linedefs, which were moved on top of existing linedefs, were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.
Fixed: Tag Explorer update fix from R2630 was accidentally placed in an UDMF-only if-block.
Updated ZDoom_DECORATE.cfg (A_WeaponOffset).
Updated documentation ("(G)ZDoom text lumps support" page).

Fixed, Tag Explorer: in some cases (for example, when geometry was removed implicitly by dragging geometry) the list was not updated.
Fixed: in some cases generalized sector effect detection logic failed to detect a valid generalized effect.
Fixed, Action selector control: action label was not updated when changing action number from one generalized effect to another.

Fixed, Visual mode: texture offsets were updated multiple times when moving texture offsets of several extrafloor sides linked to the same control sidedef.
Fixed, Visual mode: sidedef geometry of sectors affected by "Copy Slope" effect was not updated when the source slope was modified.

Added, Sound Environments mode: sound environments of the same type are now colored using the same color.
Added, Sound Environments mode: current sound environment is now highlighted (can be toggled using "Toggle Highlight" action).
Added: Tag selectors now have up/down buttons.
Fixed, Sound Environments mode: sound environments were not updated after performing Undo/Redo actions.
Fixed, Sound Propagation mode: sound zones were not updated after performing Undo/Redo actions.
Internal: moved "Toggle Highlight" action to the core, also changed it's category to "View".
Internal: "Toggle Highlight" action state is now saved in the Program configuration.
Updated ZDoom_DECORATE.cfg (GetZAt).
Updated ZDoom_linedefs.cfg (Sector_SetPortal args).

Changed, Visual mode: "Auto-align textures" and "Paste Textures Floodfill" actions now use visual mode geometry to determine whether a sidedef part should be processed. This fixes inability to apply said actions to sidedef parts only visible because of slopes.
Fixed, Visual mode: both "With same texture" and "With same height" Select modifiers are now checked when both of them are used at once (previously a sidedef part/floor/ceiling was selected when any of those matched).

Fixed, Find and Replace mode: fixed an exception when trying to assemble search result label for a named script without arguments.

Added, Find and Replace mode: action arguments are now displayed in "Linedef Action and Arguments" and "Thing Action and Arguments" search results.

Fixed, Linedefs mode: fixed inability to highlight linedefs when "Stitch geometry within" setting was set to 0.
Fixed, Visual mode: fixed a crash when performing "Auto-align textures" actions on selected sidedefs when there were also floors/ceilings selected.

Fixed: in some cases sidedefs were incorrectly reassigned when applying Edit Selection and Drag Geometry modes.

Fixed, Visual mode: rendering effects of "Slope floor/ceiling to here" things (9500/9501) should not be applied when their arg0 is 0.

Fixed, Visual mode: "Rotate CW"/"Rotate CCW" actions should update thing-based effects when used on Things.
Added/restored, Visual mode: restored "Move Texture Left/Right/Up/Down by 8" actions, added "Move Texture Left/Right/Up/Down by Grid Size" actions (default keys are Ctrl+arrow keys).
Fixed, Game configurations: Hexen's Bell actor was missing "hangs" flag.

Fixed, Sectors mode: tags and effect labels were displayed instead of selection number labels after disabling, then enabling selection numbers when there were sectors with tags or effects selected.

Fixed, Things mode: fixed a crash when switching to Things mode when more than 256 things were selected.

Added: holding Control key while switching to/from Visual mode will now temporarily disable position synchronization (works only when 'Synchronize camera position between 2D and 3D modes' Preferences option is enabled).
Fixed severe lock-up after finishing dragging many vertices/linedefs/sectors in Classic modes.
Updated documentation ("Synchronizing camera position").

Updated ZDoom_DECORATE.cfg (ALLOWTHRUFLAGS flag).

Fixed, Classic modes: fixed excessive redraws and text label / sector highlight flickering when using rectangular selection with modifier keys.

Fixed, Visual mode: in some cases translucency was ignored on inner top sides of translucent 3d floors.
Internal, Script Editor: moved some setup/auto-completion logic to separate classes.
Updated ZDoom_DECORATE.cfg (A_QuakeEx).

Fixed, Visual mode: 3d floor outer sides were not updated after toggling rendering effects off, then on.
Updated ZDoom_DECORATE.cfg (GetAngle function). 

Added, Drag Vertices\Linedefs\Sectors\Edit Selection modes: sidedefs facing outside of current selection are now reattached/added/removed after moving the selection.
Currently this will work as intended only if the selection ends up either completely inside a single sector or completely outside of any sector. Also this logic won't be applied if the selection contains the lines with only start or end vertex selected.
Internal: some TextLabel refactoring.

Added, Sectors, Linedefs, Things modes: map element selection order of rectangular selection is now direction-dependent.

Fixed, Visual mode, UDMF: in some cases Fade color was not applied to floor and ceiling surfaces of 3d floors.
Fixed, Visual mode: in some cases not all sidedef geometry was updated when updating sectors with Plane Align (181) action. Also fixed some more unnecessary geometry updates.
Fixed, Linedefs mode, Things mode: in some cases deleting linedefs/things caused a crash when trying to update text labels.
Fixed, Draw Lines mode: in some cases the drawing was prematurely finished when "Auto-finish drawing" option was enabled.

Added, Draw Lines mode: additional guidelines and horizontal/vertical line lengths can now be displayed for currently drawn line using "Show guidelines" top menu button.
Changed, Draw Lines mode: line angles are now shown only when "Show guidelines" mode is enabled.
Fixed, Draw Lines mode: in some cases "Snap to cardinal directions" mode was snapping only to diagonals.
Fixed, Draw Lines mode: snap to geometry behaved incorrectly when "Snap to cardinal directions" mode was enabled.
Changed, Things mode: dynamic light shape is now drawn using highlight color when a dynamic light thing is highlighted.
Added more sanity checks to MODELDEFS parser.

Added, Visual mode: "Increase/Decrease Scale", "Reset Texture Offsets" and "Reset Local Texture Offsets" actions now work when used on 3d floor sides.
Fixed: CVARINFO parser was unable to parse negative int/float values.
Fixed: in some cases TextLabel text size was checked before it was calculated. 
Internal, Visual mode: reduced the number of unnecessary geometry updates when changing map geometry.
Updated ZDoom_DECORATE.cfg (atan2 and VectorAngle).