I want to create a shortcut for my mouse buttons: forward and back. But can't figure out where it is possible to do..?
Shade is very keyboard centric. There are some mouse operations you can adjust in Preferences.
If you have a mouse which allows for software profiles, you should be able to associate those additional buttons with specific key commands. In Shade, you can assign keys to specific functions using the Shortcut menu item.
I don't have one myself, but I believe we also natively support the 3Dconnection devices.