Aiming through the optics of a sniper rifle (Mass Effect)

All good.
I was looking for a solution to my question - I did not find it. On a google request, "Mass Effect sniper rifle scope" gave only results about the scope swing "problem" (I don't have this problem).
My problem is the following: how to make it so that it would be necessary NOT to hold down the RMB for aiming, but aim in the "switch" mode, that is: pressed once - the sight turned on, pressed a second time - the sight turned off.
Maybe the game provides such a setting, but I did not find one. I would appreciate your help.