I was searching for this information when I found: [PART 2] How to operate ~/.XCompose with QT applications?
Here is what I did to get this working. I am on Manjaro, x86, Plasma.
Add the following to your environment. (Mine is in
GTK_IM_MODULE=ibus QT_IM_MODULE=ibus XCOMPOSEFILE=$HOME/.XCompose XMODIFIERS=@im=ibus
Run the following:
Add your custom keycodes to .XCompose. Here is mine:
# Import Default Rules include "%L" # Custom Semitic <Multi_key> <h> <period> : "ḥ" # Lowercase Ḥeth <Multi_key> <H> <period> : "Ḥ" # Uppercase Ḥeth
Then restart or reopen your GUI application.
The only other thing I did in testing this was run the following command, but it made no difference from what I can tell.
setxkbmap -option compose:capslock