Ubuntu – Shortcut keys and other issues with certain gtk apps on Wayland

Having two cursors when using a tablet in Wayland is by design, but the problem you describe could be due to the fact that you're using X applications on Wayland (using XWayland). Tablet support for X applications under Wayland will be included in the upcoming Xorg 1.20, which will be released in 2018. Until then, you're better of using Xorg. Now, I don't know or use MyPaint myself, so if MyPaint is actually a native Wayland application, my answer does not apply.

I use 3rd layer symbols and assign arrows to letters hjkl

Install gnome-tweaks tool

Inside gnome-tweaks go to Additional Layout Options and choose Caps Look as a key to choose the 3rd level.

Then open your terminal and go to /usr/share/X11/xkb/symbols/ There are all keyboard layouts store on your computer

Make a backup of your layout

cp us us_old

Modify file as root

sudo nano us

Third values in arrays are your keys:

key <AC01> {[a,A,Home]};
key <AC02> {[s,S,BackSpace]};
key <AC03> {[d,D,Delete]};
key <AC04> {[f,F,End]};
key <AC05> {[g,G]};
key <AC06> {[h,H,Left]};
key <AC07> {[j,J,Down]};
key <AC08> {[k,K,Up]};
key <AC09> {[l,L,Right]};