Used sources indication in Project window?

In your Project window right click the three horizontal lines (icon) next to your project window name and from the pulldown menu select 'metadata display'. In the window that opens twirl down the arrow for 'Premiere Pro Project Metadata' and tick 'Video Usage' (and 'Audio usage' if you want). Now, with Icon view mode for your bin, you will get small icons that appear in the bottom right hand side if each clip icon in your bin that will indicate a clip is used in a sequence. Hover over these icons to see how many times a clip is used.

You can also see 'usage' as a column in list view as well - though you'll need to also turn this on in the metadata display window.