[akirk]

I also use a QWERTY keyboard and I use a custom keyboard layout that maps alt-a to ä, alt-u to ü, alt-o to ö, alt-s to ß (plus the same for uppercase for the first 3). That works well for me without the need to post-process.

On macOS it's relatively easy to create using a tool called Ukulele (https://software.sil.org/ukelele/). You can also download my layout here: https://alex.kirk.at/USUmlaut.keylayout

[xmodem]

On macOS you can also access related symbols by long-pressing keys. Obviously for large blocks of text you're still going to want to switch layouts but for a quick IM reply or typing a couple of characters I think it's faster.

[dewey]

The faster way is to press Option + U and then the letter u for ü or a for ä. Have been using a US keyboard since before this long press feature came over from iOS and it’s way faster that way.

[RamblingCTO]

I just use "US international PC" which allows using ä etc. by typing " and then combining it with a, u etc.

[eviks]

You can do the same on Windows with an AutoHotkey solution

[sgjohnson]

I’ve done the same exact thing but for Latvian diacriticals (āčēģīķļņšūž).

The default behaviour of the Latvian layout in macOS is to make apostrophe a dead key, which really grinds my gears. So I made it alt+whatever letter instead. As a dev I use apostrophe way too much to be okay with typing '+space for it.

[eptcyka]

Would you mind sharing it?