Understanding "Add Mark"

[vlb]

I see the intriguing "Add Mark" item in my Display menu but I can't seem to figure it out. I select it; nothing seems to happen.

I expect it to add a mark at the point where my scrollbar is _now_ but it doesn't.

What does it do? And is there a way to put a mark where my scrollbar is now? Do I need to file a feature request for this?

[Robby]

This was added for 1.4 so I'll move this thread to the "Beta" section.