I would love to see a green check mark above a transition I have already used in a project, just like the ones above photos or videos or music I am using.  With so many transitions available, I jump around looking for ones I like, and I would love to be able to tell with the green check mark if I've already used one, instead of wondering if I used it or not and then trying to find out.  Or am I missing something in the program that already does that?  Thanks for your consideration.

Most people don t use so many different transitions in a project and don t need these check marks, unlike with clips.

Workaround : 

Each time you add a new transition you can rate it in the library. Therefore its thumbnail will show a little asterisk. Then it s easy to identify which transition has been already used or not.

Thanks for the suggestion, but if I do that, when I go into another project, will the asterisk still be there?  If so, would there be a way to reset all the asterisks?  I'm just trying to determine if I have used a specific transition in the current project I'm working on, not if I've ever used it.

Indeed, the asterix are not reseted if you open a new project.

My workaround is not perfect.