As a person who moved to Germany, sometimes I have to use Umlauts, but I hate the German Keyboard, especially the chaotic layout of all symbols (except letters).
So, I'm using a US keyboard layout, but with added German Umlauts via AltGr key
(yes, I have a US keyboard. If you have a German keyboard, take a look at this twin project).
The keyboard is a copy of the great work by @thomasfaingnaert, his United States (International) with AltGr dead keys keyboard, which I used before, but it always confused me to type ú instead of ü or ó instead of ö.
So, I ended up with this mix. Basically, all umlauts are now located on their corresponding letters. E.g. to type ö, you just need to press Alt Gr + o and to type Ö correspondingly just Alt Gr + Shift + Ö.
Without pressing AltGr, the keyboard has a US layout.
When you press AltGr or Shift+AltGr key, the keys are mapped as following:
You can download the latest installer from the releases tab of this repo.
If you prefer to build from source, you can open the .KLC source file in Microsoft Keyboard Layout Creator. You can use this great guide on how to work in this program. After opening the file, choose Project > Build DLL and Setup Package in the menu to create an installer.