For your consideration...try on a new mini test run project before you use it on a "real" project....
Open Project Assets
Click on its Panel Options Tab
In Panel Options select View
In View select List View
In List View all the files that are in Project Assets and are on the Timeline will have a green dot in the Used column.
If you remove a file from the Timeline, the green dot next to the file involved will disappear.
You should be able to go through the opened Project Assets/List View and Clear all those entries that do not have a green dot next to them.
Another safety net to consider....make a copy of the "real" project, and try the above on the copy.
Please let us know if we have targeted your question and if the above works for you.
ATR to the rescue once more.
This is exactly what I was trying to figure out. Thanks again.
You guys just rock.
Glad the suggestions worked for you.
We are but the back seat drivers. So congratulations on a job well done sorting through the details.