Recent versions of OS X support adding of accented characters by pressing and holding a key - a pop-up menu appears with various accent options.
Doing same in Studiometry simply triggers key repeat eventually.
Presumably part of an OS X core library Studiometry doesn't support… but perhaps when you rewrite it will come then?
This will be included in the transition from Carbon to Cocoa, as the function is built into Cocoa applications. We have been working on transitioning Studiometry and Accounted over and they will have many other benefits from the transition as well (spell check, full screen capabilities, services, generally better interface elements, more).
This has been added for Studiometry 11.
