Currently to select an action in the mouse menu you must press Enter, could you add a Control option to customize this action, and let the players able to select another key.
I liked the arma 2 system where you selected the action with mouse 1 instead of Enter.
You can customize this in the controls options. Default alternatives to Enter are Space and Middle Mouse Button. But as said you could be able to change this to LMB in the options.
ok I found a solution, in the controls options you can select either Arma 2 or Arma 3 key profils.