ARMA 3 offers an incredible freedom with regards to custom key bindings, such as allowing keys to be used in multiple ways like double tapping a key or using a combination of two keys to trigger a specific function.

Among other things, it also features the ability to use the CTRL key along with either mouse button as a key combination. Unlike any other combination of buttons, which you can assign just by pressing them in the bindings config menu, this requires dragging the pre-established "CTRL + Mouse Btn 1" combination entry from the right-hand side within the key assignment window to the main assignment window when editing a given function to assign keys to.

It would be very nice to have the ability to use the other two function keys, SHIFT and ALT, in combination with the mouse buttons in a similar manner, and therefore to have such a pre-established entry for assignment to functions as well, as manually clicking either of the keys in conjunction with mouse button 1 (or 2) will obviously not work, much like it is the case with CTRL, which appears to be the entire reason for the pre-defined entry of the combo with CTRL in the first place.

All things considered, this is obviously a very low priority issue, but at the same time, implementing this feature should cause a trivial amount of work at best, and it should be a non-controversial issue, as it's just another, additional option for more key binding combinations that become available without altering any existing features of the game.