Feature description

Currently, there is no way to lock a modifier so that it stays depressed. So if you have a key sequence you need to press multiple times, such as ctrl-n to go through auto complete suggestions in vim, you need to hit ctrl n, ctrl n, ctrl n, etc; it would be nice if you could do something like hit ctrl twice to lock it, similar to the shift key, then you could just hit n, n, n, etc.