Renamed "Set current textures" to "Set default textures" (I hope that makes more sense now).
Fixed and updated documentation.

Error Checks mode: connected lines with decimal positions were reported as overlapping in some cases.

Fixed "Snap Map Element to Grid" documentation.

"Snap Selected Vertices to Grid" mode: renamed to "Snap Selected Map Elements to Grid". Now it aligns things as well.
Edit forms: some realtime controls were applying relative values incorrectly.

Fixed a crash when executing "Toggle Geometry Effects" (Tab).

Increased maximum zoom level in Classic modes to 3000%.
Added "1 mp" option in grid size menu.
Added "400%" option in zoom menu.
Renamed "Toggle GZDoom rendering effects" action to "Toggle Geometry Effects".
Sync camera position: Visual Camera height is now changed only if camera is above or below current sector.
Classic modes: view was not redrawn after "Test map from current position" action.
"Test map from current position" action: incorrect player start was used when a map had several Player 1 Start things.

Tag and script number/name drop downs in Edit forms are now resized to match the width of the longest entry. 
Jitter mode: view was not updated when "Relative" option was toggled.

Color picked plugin: plugin used incorrect default "lightcolor" value after r1758.

UDMF fields, handled by UI, had broken field types after r1758.
Removed some redundant type casts.

"Look Through Selection" action: InterpolationPoint can be handled the same way as SecurityCamera or AimingCamera.

Visual mode: added "Look Through Selection" action (default key is "Y"). This action places visual camera at the same position as selected/highlighted thing and rotates it to match thing's angle. Special handling is available if targeted thing is AimingCamera, MovingCamera or SecurityCamera.
Script editor: pressing "F1" now opens keyword help instead of program manual.
Linedef edit form, Thing edit form: rewritten script support logic. It should now work in the same manner as the rest of controls.
Thing info panel: thing arguments now have proper labels.
Edit forms, UDMF: fields, which are handled by UI, are no longer shown in "Custom" tab.
Visual mode: fixed a crash when loading a model on a video card without Shader model 2.0 support.
Fixed incorrect argument number and changed most of labels in "Cameras and interpolation" section of zdoom_things.cfg.

ACS support: script numbers/names without space between them and script arguments (like 'script 999(void)' or 'script "test"(void)') were not parsed.

Visual mode: texture offsets are now clamped to texture size when dragging textures with mouse.
Visual mode, UDMF: when gravity is enabled, sector gravity now affects camera movement.

Textures were not loaded properly from PK3/PK7 archives.
Visual mode: restored ability to remove textures using Delete action.
Visual mode: fixed several bugs in Cut/Copy/Paste things actions.
Visual mode: vavoom style 3d floors were not displayed properly.
Visual mode, 3d floors: added support for "RestrictLighting" (2) flag.
Visual mode, 3d floors: inner sides of 3d floors with "swimmable"/"render inside" flags used incorrect brightness value.

Fixed several crashes when trying to load not existing images and models from folder/pk3/pk7 resources.

Visual mode: fixed a crash while changing 3d floor texture offsets when visual sector was not created for 3d floor's control sector.
Visual mode: Info/Warning/Error status messages were not displayed properly when nothing was selected.
Sector Edit form, UDMF: Reset and Link buttons were overlapped in Floor/Ceiling scale controls.

Textures now load up to 2x faster when "mix textures and flats" flag is set in game configuration.
TEXTUREx/TEXTURES: texture will now be created if at least one of it's patches is loaded.
Visual mode: fixed a crash when "Slope floor to here" (9500) or "Slope ceiling to here" (9501) things were not inside sector.
Fixed: flats were not loaded form wads inside Directory and PK3/PK7 resources.
Sector Info Panel, Linedef Info Panel: texture size was shown for unknown textures.

Fixed some errors in non-UDMF <-> UDMF map conversion.
Updated ISS setup script (not tested).
Removed some unused variables.

Texture scale controls now have "Link" button. 
Thing, Sector (UDMF) and Linedef edit forms now work in realtime mode.
Some more fixes in Edit form realtime update stuff.
Removed some unused variables and functions.

Sector Edit form, Vertex Edit form: fixed a crash when updating sector/vertex properties in Visual mode.
Reorganized game configurations.

Sector Edit form, UDMF: sectors were not updated properly after closing the form because of changes in Doom/Hexen Sector Edit form.

Status text now displays info about current selection.
Removed StairSectorBuilder plugin. The version form doombuilder.com works fine with current version of GZDB.

Tag Statistics form: you can now double click on Sectors, Linedefs or Things cell to select them, and right click to open their properties.
Texture size labels were displayed incorrectly in some cases.
Rewritten VerticesMode.DeleteItem() once again...
Vertex Edit form now works in realtime mode.
Vertex Edit form: ceiling and floor vertex offsets can now be cleared.
Added StairSectorBuilder plugin (I suppose some external plugins will stop working in GZDB because I've changed ButtonStep to float in ButtonsNumericTextbox a couple revisions ago...).
Preferences form: action description is now scrollable.
Changed background color of Sector Edit form.
Vertex' ZCeiling and ZFloor properties are now managed internally.

Rewrote VerticesMode.DeleteItem function. It was still not working properly after previous commit (proper vertex deletion can become surprisingly complicated in some cases)...

Visual mode: you can hold Shift while dragging a texture to lock movement to horizontal axis, and Ctrl to lock it to vertical axis.
Color Picker: fixed a crash when entered float values were not in 0.0 - 1.0 range.

Visual mode, UDMF: OffsetX and OffsetY were not properly taken into account in "Fit Texture Width/Height" actions.
UDMF: different Sector Edit Form is now used in UDMF map format.
Some fixes in Linedef edit form.
Added missing icons.

Visual mode, UDMF: added "Scale Texture Up (X)", "Scale Texture Down (X)", "Scale Texture Up (Y)", "Scale Texture Down (Y)" actions. Default keys are Num6, Num4, Num8, Num5.
Visual mode, UDMF: renamed "Rotate Thing Clockwise" and "Rotate Thing Counterclockwise" actions to "Rotate Clockwise" and "Rotate Counterclockwise". These actions can now be used to change rotation of floor/ceiling textures.
Visual mode, UDMF: "Reset Texture Offsets" action now also resets sidedef's scale and floor/ceiling's scale and rotation.
Visual mode, UDMF: control line's OffsetX and OffsetY were not taken into account when calculating texture offsets of 3d floors' sides.
Visual mode, UDMF: fixed a ton of bugs in Auto align functions.
Visual mode, UDMF: when using "Move Texture Left/Right/Up/Down by 1" actions texture offsets were not updated properly when texture's scale was < 1.0.
Visual mode, UDMF: OffsetX and OffsetY were not taken into account in "Fit Texture Width/Height" actions.
Dockers Panel: added Pin/Unpin button, which acts the same as "Preferences -> Interface -> Side panels -> Auto hide" checkbox.
Texture size labels can now be disabled by unchecking "Preferences -> Interface -> Show texture and flat sizes in browsers" checkbox.
Texture size labels now are not shown for unknown textures.
Most of texture size labels had incorrect bg color.
ZDoom_linedefs.cfg: action specials 223 and 224 had incorrect Arg0.

Visual mode: fixed a crash after disabling GZDoom rendering effects (Tab key) when visual sector was not created for sector with 3d floor's control linedef.

Fixed several bugs in Engine selector dialog ("Game configurations -> Testing").

Fixed a typo in one of Visplane Explorer messages.
Small fixes here and there.

Map Analysis mode: only a single undo is now created when multiple similar errors are fixed using "Apply to all errors of this type" checkbox, which greatly reduces errors fixing time.