here's an INITIAL version -- use with care .. it has been tested in a benign environment, but I'm fairly sure that active use will find a way to break it...
https://www.mediafire.com/file/vhxz93hn ... r.zip/file
It will run on 12.0 and later -- it is compatible with 13.5 .. only a few hours to go for that now!

What it does:
- click on a curve segment, then drag the mouse -- the segment arc will follow the mouse and the bezier handles will get updated automatically.
- the segment has six zones:
--- too close to a moho mesh point (and the tool will silently refuse to do anything)
--- in the next 1/6th of the segment - when only the nearest bezier handle will be affected
--- from there to the middle where both handles are (proportionally) affected
and the same three zones on the way to the other end point of the segment...
IOW: too close to a moho point: no action
close to a moho point -- just the one Bezier handle moves
elsewhere -- both handles move
===
I've noticed a couple of "not quite as tidy as I'd have liked" behaviours: sometimes the mouse / pointer will not stay "stuck" to the curve -- the segment still moves in response, but there's a visual gap often when the resulting Bezier handle becomes "very long" ... if this becomes a significant problem let me know please..
Unlike Krita, it does not show the handles moving; and does not give a visual indication that a segment is selected - and I'm planning on leaving it that way unless there's a clamour for such..
As ever - let me know how it works for you / bugs etc / requests for enhancements..