General interface: dynamic lights rendering mode and model rendering mode are now selected via drop-downs.
Renamed "Toggle dynamic lights rendering" action to "Show dynamic lights".
Changed: "Show dynamic lights" action now toggles between available dynamic light rendering modes.
Renamed "Toggle models rendering" action to "Show models".
Changed: "Show models" action now toggles between available model rendering modes.
Removed "Toggle dynamic lights animation" and "Render selected/all models" actions.
Fixed, Randomize Sectors form: selection highlight was not updated after applying the changes when the form was shown in Sectors mode.
Consistency: selection is now cleared after applying changes done in Randomize Things and Randomize Vertices forms.
Fixed, Classic modes: sprites of things with attached models were not rendered when model rendering was disabled.
Updated documentation.

Visual mode: "Lower/Raise Floor/Ceiling" actions now work on surfaces with sector slopes.
Cosmetic: numeric textboxes, which support relative values, now have differently colored text and a tooltip.
Internal: renamed Sector.CeilingSlopeOffset to Sector.CeilSlopeOffset, Sector.CeilingSlope to Sector.CeilSlope to match their names with similar sector properties.

Internal: added General.Interface.ActiveDockerTabName property.

Added: Map Analysis: added "Check texture alignment" check. Currently it works only in Doom/Hexen map formats.

Fixed: Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) was not working properly when used on vavoom-type 3d floor sidedefs.
Fixed: Visual mode, UDMF, "Auto-align textures" actions: vertical texture offset was calculated incorrectly for vavoom-type 3d floors.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works properly with vavoom-type 3d floors.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works when used on floors and ceilings of a 3d floor.

Visual mode: "Select" action with "with the same textures" / "with the same height" modifiers (Shift/Ctrl + LMB) now works when used on sides of a 3d floor.
Visual mode: "Select" action with "with the same textures" modifier (Shift + LMB) now selects adjacent sidedefs only when their height intersects with the height of the current sidedef.
Visual mode: "Select" action with "with the same textures" modifier (Shift + LMB) was not selecting connected one-sided sidedefs when used on a sidedef without a texture.
Cosmetic: fixed a couple of action descriptions in BuilderModes' Actions.cfg.
Cosmetic: MainForm.UpdateToolStripSeparators was working incorrectly in some cases.
Cosmetic: ErrorChecksForm's title was not updated when no errors were found.

Preferences: added "Vertex scale (3D)" preference, renamed "Vertex scale factor" to "Vertex scale (2D)".

Game Configurations: changed default map name for Doom maps to "E1M1".
New Map Form: "E1M1" is now used as a default name for Doom maps.
Thing Browser Control: double-click event is now sent only if user clicked in the node's label area.
Interface: added info messages for several toolbar toggles.
Interface: made Brightness icon more readable when using dark windows themes.

Visual mode, UDMF: added some boilerplate to prevent invalid sector slopes from showing up/crashing the editor. 

Fixed: MapSet.GetSectorByCoordinates() returned "false" in some cases when a given coordinate was on top of sector's vertex.
Internal: UDMF sector slopes and offsets are no longer stored in sector.Fields. Use sector.FloorSlope, sector.FloorSlopeOffset, sector.CeilingSlope and sector.CeilingSlopeOffset.

Visual mode, 3d floors: fixed broken 3d floor visibility detection (which failed in some cases when real floor or ceiling was sloped).

Visual mode: some parts of 3d floor were shown even when it was above real ceiling/below real floor.
Visual mode: real floor was colored by 3d floor's color even when it was below real floor.
Action Browser form: keyboard focus is now set to Filter text box by default.

Visual mode: unrelated sidedefs were selected when trying to select empty texture using "Select with the same textures" action.

Visual mode: middle sidedef geometry of single-sided linedefs was rendered differently than in (G)ZDoom in some cases.

A r1959 change in ImageSelectorControl prevented inherited classes from showing properly in Visual Studio's designer.
Also made a bunch of methods static.

Preferences: added "Capitalize texture names" option (located in Preferences -> Appearance -> Additional options). When disabled, the casing of displayed texture names will match filenames for textures loaded form TEXTURES or pk3/pk7/folder resources.
Textures Browser: added support for displaying long texture names.
Errors list is now cleared when reloading resources.
Visual mode: added basic support for sector slopes (no UI for that feature yet).

One of Thing Statistics form's columns was editable for no good reason.

UDMF: sector, linedef and thing render styles are now defined in Game Configuration.

Thing Edit Form, UDMF: added controls for setting pitch, roll, scale, render style, fill color, alpha, health and score.
Visual mode, UDMF: UDMF scale is now applied when rendering sprites.
Added Thing Statistics form (Edit -> View Thing Types...), which shows all loaded thing types with some additional info.
Visual mode: sprites with negative ScaleX and positive ScaleY were not rendered properly.
Classic modes: display was not updated after loading a sprite.
Current testing engine change was not saved on closing the program when no other game configuration settings were changed.

"Rotate Clockwise" and "Rotate Counterclockwise" actions now work in Things mode (they will rotate things) and in Sectors mode (they will rotate floor/ceiling textures based on current view mode).
Moved "Rotate Clockwise" and "Rotate Counterclockwise" actions to "Edit" category.
Tag Statistics form: help label was incorrectly aligned.
Some actions in Sectors and Linedefs modes were not used on highlighted map elements.
Some actions in Sectors and Linedefs modes created undo groups incorrectly when used on highlighted map elements.

Replicated Doom texture vertical offset glitch when front and back sector's ceilings are sky.

Linedef Edit Form, Sector Edit Form: when several map elements with different textures are selected, the "texture stack" icon is shown in the texture selectors instead of the "missing texture" icon.
Error Checker mode: added "Check missing flats" check.
Error Checker mode: fixed several descriptions. 
Sprite patches for sprites defined in TEXTURES are now loaded from Sprites namespace.
Some of my older texture alignment code didn't work properly when strict texture/flat handling ("mixtextureflats" game configuration flag set to false) was enabled.
Fixed some incorrect checks for missing texture ("-").

Added "Full Brightness" toolbar button and "View" menu item. These call "Toggle Full Brightness" action.
Added "Make Door" menu item to "Sectors" menu.
A warning is now displayed when "Make Door" action is called without a selection.

When you try to change floor/ceiling texture offsets in Doom/Hexen map formats, a warning is displayed in status bar (instead of spamming you with message windows).
Mode actions toolbar is now auto-hidden when there are no buttons to display.

Game configurations: added "fixedrotation" property to dynamic lights, which use the angle property as a parameter.
Maintenance: removed a ton of redundant stuff.

Game Configurations: added support for new property "fixedrotation", which keeps thing's angle constant when a thing is rotated in Edit Selection mode.
Game Configurations: added "fixedrotation" property to "Polyobject Anchor" (9300), "Polyobject Start Spot" (9301), "Polyobject Start Spot (crush)" (9302) and "Polyobject Start Spot (hurts to touch)" (9303) actors.
Color Picker plugin: moved plugin button to "Modes" toolbar group.
API: added ToolbarSection.Modes property, which can be used in MainForm.AddButton() to add a button to Modes group.
Removed a bunch of unused variables.

Configurations: increased game configuration loading speed (in previous builds it took ~650 ms. to load a single game configuration, now it takes ~120 ms. to load all 64 of them). As a side effect, New\Open Map Options, Map Options and Game Configurations windows are now opened noticeably faster. The editor starts up a bit faster as well.
Configurations: all 64 game configuration are now available by default.
Game Configurations window: game configurations can now be disabled. This setting is mostly cosmetic. When a game configuration is disabled, it won't be shown in "game configuration" dropdowns in New\Open Map Options and Map Options windows. If a map's .dbs file specifies a disabled configuration, it will be picked as a map configuration anyway.
Linedefs mode: vertex insert preview logic used Highlight range instead of Stitch range (which is used when draw mode engages).
Visual mode: double-sided middle textures were not selected when using "Select" action with "with same texture" modifier.
Textures: some optimizations in patch blending code.
ZDoom ACS script configuration: added definitions for StrLeft, StrMid and StrRight functions.

Map Analysis mode: "Check overlapping lines" logic was broken on maps in Doom and Hexen map formats.
Map Analysis mode: "Check overlapping lines" now finds duplicate linedefs (e.g. when 2 lines have the same start and end positions).
Map Analysis mode: added "Check overlapping vertices" check. This will check if a vertex is on top of a linedef or another vertex.
Some cosmetic changes in Tools and BaseVisualMode.
Updated zspecial.acs

Visual mode: when changing height of a triangular sector all vertices of which have height offset, vertex heights will be changed instead of sector's floor/ceiling height (this allows to edit terrain without the use of vertex handles).
Visual mode: "Copy Texture", "Copy Texture Offsets" and "Copy Properties" actions now always copy properties from currently highlighted surface (previously they copied properties from the first selected surface when something was selected).
Draw Rectangle mode: nothing was drawn in some cases.
Drag Things mode: grid was not updated when grid size was changed in this mode.

Numeric textbox: in addition to '++NN' and '--NN', you can use '*NN' and '/NN' to multiply or divide the values.
Configurations, ZDoom_linedefs.cfg: some linedef action arguments were missing a proper type.
Rewritten parts of hints system. Hints are now loaded from "Hints.cfg" file.

Added ThingSlope patch by Boris (adds support for Sector tilt things (9502 and 9503) in Visual mode).

Visual mode, "Select" action with "With the same texture" modifier: sidedefs are no longer selected when matching part has zero height.

Visual mode: using "Select" action with "select with the same texture" modifier in some cases selected middle texture when it shouldn't have.