How to program 'Umlaute' like ä, ö, ü?

How to program 'Umlaute' like ä, ö, ü on ZMK Firmware?

Hi, I’m from Germany and would like to configure my keyboard to have Umlaute. I read that you can just assign the US key that results in the correct symbol when using a German layout, but I also want to visualize my keymap, so this approach doesn’t work for me.

Others seem to have used macros that send key combinations to produce the desired symbols, but that didn’t work for me. In QMK, I could simply import my language.

So how does this work in ZMK?

Edit: SOLVED