Map Analysis Mode: checking for missing activation flags (UDMF) now finds linedef that are missing an actual activation flag, not only lines without any flags in that group. Fixes #288
Linedef Editing Form (UDMF): now only missing required activation flags are marked red

Added support for only enabling editing modes when the current game configuration supports the features. Currently only applies to 3D Floor Mode, Slope Mode, and Draw Slope Mode. Fixes #463

Slope Mode, Draw Slopes Mode: both modes are now deprecated as they are superseded by visual sloping. The modes will be removed in the future. Entering the modes will add a warning to the Errors And Warnings dialog

3D Floor Mode: added option to use Synchronized Things Editing when (de)selecting sectors. Resolves #443

Visual Mode: fixed inaccuracies of when upper/lower textures are shown when sky rendering is enabled

Fixed a bug where pasting texture offsets in UDMF configurations without support for local sidedef texture offset (like the Eternity UDMF configuration) didn't work. Fixes #538

Fixed a bug where trying to align the grid to a linedef or setting the grid origin to a vertex would crash when no map was opened. Fixes #536

Such an event invokes every unbound action.

Eternity Engine configuration: moved portal related sector flags to the portals tab of the sector edit form

Sectors Mode: fixed a crash when merging sectors while a shared linedef between them was shown as an association

Fixed a bug where saving WADs that didn't have their data starting right after the header would corrupt the file. Fixes #531

Map Analysis Mode: fixed a crash when the sidedef of 1-sided lines had upper/lower textures defined. Fixes #533

Using the "Reset plane slope" action now sets the floor or ceiling heights to the height of the plane at the sector's bounding box center

Fixed a bug where resetting the ceiling slope in the UDMF sector edit form would invert its original height

Error Checker: added config options to ignore unknown textures on sidedefs for certain actions. Resolves #518

Find and Replace Mode: fixed a bug where searching for linedef or thing action and arguments would not show "0" as an argument if it was the last arguments. Fixes 528

DECALDEF parser: fixed a problem where opening curly braces in the same line as a decal definition caused a parsing error

Decorate/Zscript Actors that replace other actors should now display the correct actor name given through the $Title editor key. Fixes #122

Added option for special handling of triangular sectors when doing visual sloping. When enabled it'll always select an opposite smart pivot handle. Enabled by default, can be disabled in Tools -> Preferences -> Editing -> Opposite side/vertex is smart pivot handle on triangular sectors