It's worth noting that the concept of a "Compose" key seems to have originated on DEC's specialized word-processors (physical machines which just did text editing), and that when Windows came on the scene, someone at DEC created "COMPOSE.EXE" which brought that functionality to Windows --- it continued working up through very late Windows 95 betas, then was broken and never updated.

There was a replacement in "AllChars" which is still on Sourceforge: https://sourceforge.net/projects/allchars/ but hasn't been updated for a while.

Looks like:

https://wincompose.info/

is up-to-date, and if I wrote more, would definitely try out, but these days, either I write the accented character w/ a stylus, type out the LaTeX command, or use the on-screen keyboard via touchscreen.