Yesterday we finally merged the work by Carlos Garnacho for support of tablet pad's buttons directly in GIMP. Basically instead of assigning shortcuts system-wide to a tablet button (then customize shortcuts in GIMP), you can directly assign GIMP actions to specific tablet button.

This only works for Wayland so far.

Carlos was detailing this work on this blog post: https://blogs.gnome.org/carlosg/2023/06/16/getting-the-best-of-tablet-pads/