Added, action argument inputs: added "<" and ">" prefixes. These decrement/increment given value by selected map element number.
Changed, action argument inputs: "+++" and "---" prefixes now do the same thing as they do in other numeric controls (e.g. add/subtract given value multiplied by selected map element number to/from initial value).
Changed, action argument inputs: changed value colors, added tooltips.

Probably fixed probable I/O race condition when loading images.
Fixed Visual mode stuttering due to floating point precision degradation when running the editor for several days without restarting (internal timer is now reset when saving the map or creating a new one).
Fixed, Nodes Viewer, cosmetic: Nodes Viewer window position was reset after pressing the "Rebuild Nodes" button.
Added Eternity Game configurations by printz.
Updated ZDoom_ACS.cfg (CheckClass).
Updated ZDoom ACC (CheckClass).

Updated ZDoom_DECORATE.cfg.
Updated ZDoom_ACS.cfg.
Updated ZDoom ACC.

Fixed: in some cases dragging lines shorter than 1 mu or vertices belonging to such lines resulted in an infinite loop.

Fixed, map element dragging: in some cases sector properties copied from incorrect sectors were assigned to new sectors when using "Merge Dragged Geometry" mode.

Updated ZDoom_DECORATE.cfg.
Updated ZDoom_ACS.cfg.
Updated ZDoom ACC.

Fixed, MODELDEF parser: forward slash in Model/Skin/SurfaceSkin paths wasn't supported.

Added, Visual mode: added support for "Change Floor Brightness to this Brightness" and "Change Ceiling Brightness to this Brightness" Boom actions.
Changed, Sectors mode: "Flip Linedefs" and "Align Linedefs" actions will no longer flip single-sided linedefs with only front side.
Fixed, Script Editor: fixed a crash when trying to update script navigator combo box when switching to a never saved ACS script.

Fixed, Visual mode: "Transfer Floor/Ceiling Brightness" actions were resetting sector color on target surfaces.
Updated ZDoom_DECORATE.cfg.

Changed: optimized generated voxel mesh size. Pro: they occupy ~50% less memory. Con: voxel loading takes ~30% more time.
Changed, Browse Textures window: several textures with the same name were displayed in "All" texture set when overriding WAD textures by Folder/PK3 textures.

Changed, Visual mode: increased maximum rendreable dynamic lights count to 64.

Fixed, Draw Geometry modes: fixed a crash when moving the mouse cursor over a vertex while holding Alt-Shift keys when there were no new points drawn in current mode.

Changed: LOKCDEFS keys are now sorted alphabetically.
Fixed, MAPINFO parser: blocks inside map definition block were parsed incorrectly when using new MAPINFO format.
Fixed, rendering: custom MODELDEF scale was applied incorrectly when "Stretched view in visual modes" option was enabled.
Updated ZDoom_DECORATE.cfg.
Updated GZDoom_MODELDEF.cfg.

Added "flagsrename" Game configurations property. It allows to override Thing flag names for specific things.
Added, Automap mode: added "Show locks" button (available in Hexen and UDMF map formats only).
Updated documentation.

Changed, Game Configurations: changed "basegame" value type from int to string.
Updated documentation.

Fixed, DECORATE parser: the parser was unable to process several quoted strings not separated by at least one space/tab char.
Fixed: the editor was unable to find actor sprites defined in TEXTURES.

Added, DECORATE: added "//$ArgNRenderStyle" special comment. It allows to specify a rendering shape to display the value of given argument. Supported values are "circle" and "rectangle".
Added, DECORATE: added "//$ArgNRenderColor" special comment. It allows to specify a color used by the rendering shape.
Updated documentation.

Added, Visual mode: added support for ROLLCENTER sprite rendering flag, updated ROLLSPRITE implementation.
Fixed, DECORATE support: the editor was unable to determine actor sprite when the actor itself had no sprites defined and the actor it inherited from was only defined in the game configuration.
Fixed, Drag geometry modes: linedefs without both sides were removed after dragging them when "Replace with Dragged Geometry" mode was active.
Updated ZDoom_DECORATE.cfg.

Added: preview sprites are now generated from voxels. Those are used as previews and when model rendering is disabled.
Fixed: voxel support logic was outdated, which in some cases resulted in voxels not being loaded and in some weird behaviour when trying to change pitch/roll of associated things.
Updated sprites lookup logic. Now it correctly handles sprites named like NNNNA0B0.
Fixed: in some cases DECORATE parser was unable to correctly detect sprite name & frame(s) block.
Updated ZDoom_ACS.cfg.
Updated ZDoom_DECORATE.cfg.

Fixed, Edit Selection mode, DB2 bug: in some cases "Flip Selection Horizontally" / "Flip Selection Vertically" actions were incorrectly flipping linedefs, resulting in broken sector geometry.

Visual mode: modified sidedef texture UV calculations to use integral linedef length to match (G)ZDoom way of rendering them.
Visual mode, UDMF: "Auto-align textures" actions now use integral linedef length when calculating texture offsets.

Added, Visual mode: added support for FLATSPRITE, ROLLSPRITE, WALLSPRITE and DONTFLIP sprite rendering flags. Removed the older GLOOME-specific implementation.
Changed, "Align Things to Nearest Linedef" action: the action can now also align things with FLATSPRITE and WALLSPRITE flags (previously only things with attached models were aligned).
Changed, "Align Things to Nearest Linedef" action: the action can now align things to the middle part of double-sided linedef, if it has a middle texture assigned. 

Added, Find & Replace mode, UDMF: added Linedef activation flags to the "Find Linedef flags" search mode flags list.
Changed, Sound Propagation mode: all sound zones are now shown when no sector is highlighted.
Changed, Sound Environments mode: the mode is now available only in UDMF map format.
Changed, Color Picker plugin: the plugin functionality is no longer available in Doom map format.
Restored the ability to create superimposed lines by dragging them with "Snap to Geometry" mode disabled.
Fixed, Sound Propagation mode: fixed a crash when a single-sided linedef had "Block Sound" flag.
Fixed, Find & Replace mode: in some cases "Find Sector/Sidedef/Linedef/Thing flags" search modes failed to find map elements with required flags.
Fixed, Edit Selection mode: in some cases incorrect geometry was created after applying multipart sector edit when "Replace with Dragged Geometry" mode was enabled.
Fixed a crash caused by eventual GDI font objects overflow.

Fixed, DB2 bug: temporary map file was growing in size after every map save/test, which eventually resulted in integer overflow exception when the file size reached ~2Gb.
Fixed, Draw Geometry modes: fixed a crash when moving the mouse cursor over a linedef while holding Alt-Shift keys when there were no new points drawn in current mode. 

Changed: single-sided linedefs with only back sidedef present are now automatically flipped when loading a map.
Changed, "Flip Linedefs" action: the action will no longer flip single-sided linedefs with only front side.
Fixed a crash when trying to determine sprite angles when images with non-sprite names, starting with expected characters, were present in the Sprites namespace.

Added, Search and Replace mode: "Find Sector Brightness" search mode now supports "<=", "<", ">=" and ">" prefixes.
Fixed, Sound Environment mode: fixed several cases when single-sided lines with only back side could cause either logic errors or crashes.
Fixed, Automap mode: fixed several cases when single-sided lines with only back side could cause logic errors.
Debug: added some debug code to WAD.Insert() to investigate the issue when lumpoffset could become negative.

Reverted some older changes to Linedef.Join(), which were made for older version of "enhanced" map element merging logic and in some cases were causing incorrect geometry to be created when using current merging logic.

Fixed: in some cases incorrect Script Configuration was used to compile scripts when performing "Save Map" / "Test Map" actions.

Fixed, Find & Replace mode: fixed a bug when "Find Sector Effect" search mode returned all map sectors when the effect to find was not generalized.
Updated ZDoom_DECORATE.cfg.

Fixed: parts of UniFileds.UniValuesMatch() logic were inverted. In some cases this resulted in incorrect behavior of "Select Similar" action in UDMF map format.
Fixed, UDMF: alpha should be ignored when applying sector fade/light color gradients.
Ported eevee's fix for incorrect sector geometry occasionally created after dragging map elements (more info: https://github.com/sirjuddington/SLADE/issues/542).

Added partial "LightMode" MAPINFO property support. Currently only "Standard" and "Doom" light modes are supported.
Updated Zandronum acc.
Updated Zandronum_ACS.cfg.

Changed, Visual mode: "Paste Selection" action (Ctrl-V) can now paste both copied textures and things, based on what was copied last.
Changed, Map Analysis mode: the view is now much more zoomed after clocking on a "Check very short linedefs" error check result.
Removed single testing engine launchable by the editor at once limitation (it worked properly only when using Test map actions anyway).
Fixed: re-did the fix for invalid geometry created when drawing very large grids from R2653, because it caused other issues.

Added, Automap mode: added "Show secrets" top menu button.
Added, Automap mode: added "Color preset" top menu drop-down.

Changed: "Unable to save the map: there are too many unique sidedefs!" error message now displays info about sidedefs counts before and after sidedef compression.
Fixed, Draw Grid mode: in some cases invalid geometry was created when drawing very large grids.
Fixed, Things mode, "Rotate Clockwise" action: fixed inability to change thing angle from 0 to 315 when "doomthingrotationangles" Game Configuration property was set to true.
Updated ZDoom_DECORATE.cfg.