gkbd-keyboard-display should distinguish dead keys
gkbd-keyboard-display -l "gb(extd)"
doesn't distinguish dead keys such as dead_grave
or dead_tilde
from normal keys such as grave
and asciitilde
. This is important information to show to users who understand dead keys, and even more to users who don't understand dead keys!
For comparison https://kbdlayout.info/kbdukx (diagram for similar Windows layout) shows dead keys with a blue blackground: