The smart component slider (the new one from Glyphs 3) resets its value while sliding. The oder methods – changing the transformation box of the component and invoking the old smart component slider dialog – continue to work.
Here is the test file from the movie above:
Test.glyphs (6.9 KB)
Glyphs 3.0.3 (3061), macOS 11.2 (20D64)
Follow up: Initially the Smart Settings are at the very bottom of the sidebar, but once the slider is dragged, the section jumps up:
I fixed the resizing issue already 
I thought you where busy breaking stuff:
But fixing stuff is also good 
I need it to crash in the debugger to be able to fix it ;(
When I read that comment I was in shock. Enabling the debugger fixes the issue? Maybe the debugging suite loads some imports that would otherwise be necessary and so it only works when debugging? Still – that reality scares me.
Can confirm 3062 fixes the issue for me. Thank you!