Another fun diacritic is the macron. The Mc in McCormick replaces Mac, and can use the COMBINING MACRON BELOW (◌̱c). I couldn't get it working in ConTeXt, so wrote my own:

https://gitlab.com/DaveJarvis/keenwrite-themes/-/blob/main/b...

When typing prose into my novel, if I use any of the words listed in the replacement text (McGenius, McNester, etc.), they get replaced with the C macron.