A line in the source monitor that shows what parts of a clip you've already used in your sequence.

[core787]

It would be great to have a thin line, similar to the duplicate frame marker, that showed you segments of your source clip which are already being used in the sequence thats open in the program monitor. 

I've attached an example. 

[Mike Dziennik]

Not quite the same thing but you can enable the 'Video Usage' column in the project panel and it will give you a dropdown of the times that clip is used in a seq.

 

[Warren Heaton]

@core787 

I can see how this would be helpful.  I've upvoted it.