It would be very great to be able to switch windows inside UE4 with the mouse that have the buttons for.
4th/5th mouse buttons aka Forward/Back buttons are used for switching windows tab in a lot of software nowadays.
Also CTRL + W is used to close a window, rarely used by software but very useful for mouse with a lot of buttons to bind.
Else for saving a blueprint or whatever, CTRL + S is the way to go 