@erin_kitsune If it were Windows only I'd suggest something using .NET, but if it needs to support Windows and MacOS the you're probably looking at a cross-platform toolkit like Qt or GTK (which also support Linux), and whatever languages work with them (which is quite a few). Qt supports C++ natively and second-best is probably Python. GTK is C-native. But again, both have a lot of different language bindings.
Or you could go the route of creating a desktop web app using Electron with HTML, CSS, and JavaScript.
@faoluin it has to be cross platform. C++ is a good idea for sure; just need a gui component for it
@faoluin @erin_kitsune concur fully there, Qt would fit that description very nicely :)