It’s easy on mobile and less so on my Mac, so I do it more on mobile. I grew up writing British English (and French), in which reorbit and cooperate are a thing, but they get systematically misread in American English, and re-orbit and co-operate look messy.
I’ve also noticed when I add a diaresis my iPhone has less of a tendency to fuck with the word after it’s been typed.
Do you have this set as autocorrect or do you type the ö each time?