One cannot bind same key/mouse button to 2 or more actions anymore so that it functions properly. Binding does get saved but only one action can be performed unfortunately.

This is beneficial to bind lets say walk and raise weapon to the same key to move slowly and ready weapon at the same time in time of high stress situation without having to press multiple keys / mouse buttons to achieve the same simple thing.

You should just follow Arma 3 way to allow player to really utilize PC keyboards and mouses to create what ever key configs to best suite players.