[Kripá Pizzorno]

James, not sure if this will help, but if you toggle from List View in the Browser to Thumbnail View, a date & time stamp is shown under the project icon. As far as I can tell, the date/time the project was last opened will be shown. (So this doesn’t help if you are opening the various projects, looking for the most recent edit, as then FCPX will show each one as having today’s date.) Hope that makes sense, and I apologize if I missed the point of your question.

[Kripá Pizzorno]

I was just trying to stabilize a compound clip today, and ended up doing what Jeremy suggests: exported a master file, re-imported, and was then able to add stabilization. Not a bad work-around.