Changes:

User interface has been refreshed.
Preferences window has Layout setting with Desktop/Laptop/Classic/Custom options.
Mixer sections can now have 3, 4, 5 or 6 effect slots (the 4 and 5 options have been added).
Small buttons are larger.

Preferences window has Name Width setting to control width of track name boxes.
Track editors can now be opened by clicking the Editor Preview pane.
Audio editor data appears much faster. It also works better with looping.
The level meters are now between the Rec buttons and the faders.
You can now right click a meter to change its size (Small / Large / Huge).
Effect/Instrument slots now show the first 4 or 5 characters of the plugin name instead of "VST" etc.
Effect Bypass buttons can be toggled by clicking the bottom left corner of the effect slot.
On larger screens the transport controls are in the middle instead of on the right, so they're closer to the track Rec buttons etc.

The current value of knobs (and faders) appears above the knob rather than below, so they're no longer covered by a mouse pointer, pencil or hand while moving the knob.
You can use Click...Shift+Click to toggle buttons on a range of mixer sections. Applies to Play, Rec, Mute, Edit and Collapse buttons and the Editor Preview panes.
Some names changes: "Cycling" is now "Looping", "Content Panes" are now "Editor Preview panes", "VST Scaling (ugly) " is now "Plugin Scaling (blurry) ".
Windows: VST plugins can be scaled individually, so you don't have to use the "Plugin Scaling (blurry) " option from the Preferences window.

Windows 11: updated menus, fixed some missing round window corners.
Windows: now requires Windows 7 or newer.
Improved VST3 window resizing.
Compressor: curve and history displays more accurately represent what's going on for Vintage and Vintage Warm programs.
Audio track data that appears on the Overview Bar while scrolling editors now takes the track editor's vertical zoom setting into account.
MultitrackStudio Remote: audio track data that appears during rewind/FF now takes the track editor's vertical zoom setting into account.
The Loop button is now disengaged automatically if it was engaged automatically. This happens when you've used Alt+draw to define the loop region, and when you've pressed F6 to play the selected part of an editor.
Added L+Left/Right keyboard shortcut to go to loop start/end point.
Editor right click menus now have 'Play Looping' (F6) option to loop selected part.
Overview Bar / Grid Bar: Removed the 'click-and-drag' way of loop region selection (nobody liked it).
Overview Bar / Grid Bar: Drawing loop range with Alt (or L) modifier now also works outside the thumb. And it can now be used while tracksport is running.

Overview Bar / Grid Bar: Double click to start now also works outside the thumb.
Overview Bar shows the current editor view area while the editors are scrolling horizontally.
Pianoroll: step recording works a bit different: Ctrl/Cmd=add note, Shift=add rest, Alt=reverse direction.
Some keyboard shortcuts / mouse modifier keys changes to make them easier to memorize ('A'=All, 'C'=same Color, 'L'=Loop).
Dropping MIDI files with SysEx-only streams on editors works better.
MIDI file import: markers are ignored if there are more than 20.
Fixed some VST3 and LV2 plugin bugs.
Fixed: Matrix Keyboard produced notes with extremely low velocity.
Fixed: MultitrackStudio Instruments: "Strength" knobs didn't work.
Many other small improvements and fixes.