Media Bin
 

In the Thumbnail view, how do I tell which clips in the Media Bin have been added to the timeline? When I'm working with 100's of clips, I get lost, and lose track.

Changing over to detailed list ?

Yes, in the detailed view.

How does it work in the thumbnail view, which I use most often?

You must be in the detailed view to see how many times you used your clips/music/video etc....

Click the "Use Count" tab to sort (from the most used, or from the smallest used).

There you can see how many times you used your media.

Don't think it is possible to see Use count in thumbnail view...

In the detailed view I get totally lost when using 100's of clips. I need to use the thumbnail view.

Well... You have to shift over between detailed view and thumbnail view...
Nothing else i could think of...

I use the "Find Unused Media" tool in Excalibur. It will take all unused clips and add them onto a new track.

Search media bin by right click and select less than 1 in use count. A great asset I just found out about. You can search for all different attributes and
even search your search bins.