Dead keys problem (Spanish layout) - Manjaro with KDE Plasma

[notNotAvailable]

/etc/X11/xorg.conf.d/00-keyboard.conf

Apparently, this Aug 2021 issue also mentions a necessity to manually edit that file:

Anybody else having keyboard settings problems?

I’ve only really noticed this after the 2021.08.09 Stable Update, but apparently many keyboard settings were changed with said update. One of them was the system-wide delay and rate settings for key repeats, which I’ve now readjusted via the Keyboard Settings section under the “Manjaro” header in System Settings. However, the following two issues have also managed to sneak in… The Compose key no longer works. On my keyboard, using the Belgian layout, I had set it to the right-hand Win-key.…

(Is this a weak point in Plasma KDE + Manjaro?)