Hey! Thanks for the note. Even as the author of ViEmu, I'd love to have support for it, since I am a heavy user of OneNote myself. But unfortunately, supporting it is out of scope. The effort to support a new application is huge, the skills required are hard to find (so you can't hire a junior dev to do it), and the sales are not huge, so the business case is very thin to non-existent. That is why there are no other emulators like this out there. I plan to maintain the current ViEmu editions, but unfortunately I'm not planning to add support for more applications.

As an example of how arbitrarily hard this can get, just think that OneNote notes are not necessarily "text", but they can have any number of free floating "text boxes" in a note, apart of course from all the pictures, checkboxes, etc... mapping this to vi/vim's world of "text lines" requires a lot of architectural thought and design -- supporting Word's understanding of what a "document" is was quite hard, this would be harder even. And you get no help from the app host, their SDKs are usually either non-existent or very limited, and you have to depend on low-level hooking, interception, heuristics, etc...

I have some idea on how to address this in the future and provide a better solution for everyone interested in vi/vim emulation for more applications, but this will have to wait until I have more resources!