First, I'd like to know more about the situation you would use this because I don't see the point right now. Let me explain: If you're in Sing-Mode. You're playing the song and somehow, a line is late. You would Ctrl-click on it? It's already too late, No? And if you know that you'll need to click on it, why not go in Edit-Mode to do this?

I really like the distinction between Sing-Mode and Edit-Mode: There's no reason to be concerned to "modify" anything as long as you're in Sing-Mode. What you're asking is to change that behaviour and I reluctant to do this.

BUT, I guess it wouldn't be difficult to do something like: When you press Ctrl-Click, the plugin switch to Edit-Mode and then do what you ask for: insert or modify the timestamp on that line.

How would it be?