SUMMARY
Touch gestures are currently very limited, most impossible to reassign, and missing vital features.

A particularly major issue is the possibility of getting stuck in a fullscreen window on a touchscreen. Touch gestures to exit fullscreen and/or close the window are vital to fix this. 

Touch screen gestures should all be assignable. There are two possible types of gesture, 1: affecting window below gesture and, 2: gestures that behave as keyboard shortcuts, applying globally or to the current window. If they behave like keyboard shortcuts it also makes sense to be able to assign them to anything you'd be able to assign a keyboard shortcut.


Gestures that can be set to affect window below the gesture OR act like a keyboard shortcut:
• 3/4/5 finger swipe left/right/up/down
• 3/4/5 finger pinch 
• 3/4/5 finger expand (reverse pinch) 

Gestures that can only be applied to a specific window (unless somebody can think of other uses):
• 3/4/5 finger drag. Each of these might make that same number of fingers swipe impossible, but that's OK – 4 and 5 finger gestures are much easier on a touchscreen than touchpad, which gives you options. The functions you would be able to assign to a multi-finger drag are pretty limited but can be very useful (e.g. move window with a 3 finger drag).

Gestures that can only act like keyboard shortcuts:
• Swipe from edge of screen.


Possible Defaults:
Move window below gesture: 3 finger drag (since 3 finger drag is enabled this would prevent 3 finger swipes from being used for anything)
Show/Hide window decorations: 3 finger pinch
Close window below gesture: 4 finger pinch
Toggle fullscreen for window below gesture: 4 finger swipe up
Maximise window below gesture: 4 or 5 finger expand
Minimise window below gesture: 4 finger swipe down
Access Overview: 5 finger swipe up
Switch between virtual desktops (left and right): 4 finger swipe left/right
Force show/hide virtual keyboard (not a current feature of Plasma as far as I am aware but a sensible one): Swipe up from bottom of screen


SOFTWARE/OS VERSIONS
NixOS 24.11 (unstable channel)
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0 
Qt Version: 6.7.1