I'm not sure how you could add this (easily), but I am wondering if you could add some type of Window Hook event to BFS so that a trigger (such as Window Created) could setup a Window Hook for the new Window, calling a C# function and then modifying/capturing Window events.

A generic Window Hook that captures all Window events would be nice (imagine implementing Spy++), or maybe one with some type of class filter would be fine. Perhaps something like SetWinEventHook or SetWindowsHookEx? Something like a simplified version of SpyWorks perhaps?

Imagine I was trying to convert minimize button right-clicks to be Minimize to Tray

I would want to look for a WM_NCRBUTTONUP message with a HTMINBUTTON wParam and call Minimize to Tray.

I figured you are already injecting a DLL into every process with Windows anyway...

Yes, I think bridging over from the injected native code DLL to a managed code event or function call is they tricky heart of what SpyWorks does