Not strictly proton, but for wine, you can see here (https://appdb.winehq.org/) that it supports more than just games.

Notpad++ works in Wine. And I used to run JMP 10 with wine too (data plotting software). Neither required Proton though.

On top off my head is the old non UWP version of Photoscape which I use from time to time to do basic edits.

Then Finale notepad for music transcribing stuff

I use to use MSOffice 2007 but recently I have switched to OnlyOffice

Although most of them, or atleast what I know off, are made for older version of windows

I’m far from an expert but I believe Proton is specifically intended to provide compatability with Windows gaming tech like DirectX.

For regular non-game software you don’t need that tech, you can just run it through Wine itself (Proton is built on Wine). Bottles is actually what I see recommended these days (it simplifies management of Wine prefixes) and supposedly many apps can run in a few clicks.

I dunno about Proton but I’d assume do. I have some CAD and 3D software I use in Wine.

Lots, but if they interface with usb (like an image writer or mouse software) it won’t work.