CtrlCore now supports those additional mouse buttons that are on the side of the mouse and have forward/backward meaning.
Pressing translates to Key events with K_MOUSE_FORWARD and K_MOUSE_BACKWARD keycodes.
The CtrlCore supports this in Win32 and Linux/gtk. I will check MacOS later...
On application side, so far I have added support to:
theide navigation
helpwindow navigation
backward button does "dir up" in filesel - that is temporary solution, filesel will need history added for the full support...
Please suggest other widgets / situations which would benefit from these buttons!