Unreal engine for making office programs

While it’s possible to use UE4 for a such thing it’s still a total overkill if no heavy or shiny visualization is not needed. The comparison posted by is a very good one.

You would want to make the desktop apps with component/event based systems and not with a game engine essentially running a game loop. On top of everything the extensibility and library support for various features are far better with the apps made for the purpose.