I never used Karabiner’s mouse movements, but I did love its sticky keys. Karabiner Elements finally supports them again on new versions of macOS. Have you tried it to see if the mouse movements work?
Last I looked Karabiner-ELEMENTS did not have this mouse-key feature. Karabiner mouse-keys really works amazingly well, so well in fact that I was willing to downgrade both my MAC's macos to be able to keep using it until my own fully replaces it !
