I think the simple answer is no.
One way see all the tags used on the screen x is to edit->select all and then right click on any selected object and choose to change tags. It will bring up a listing of all tags (I think it shows 10 at a time??)
If you truly want a "dump", you could create a new WW app and import screen x from your original app to the new app. I think you need to verify all the imported tags (maybe edit-> select all, then right click and change tags, accept all tags - something like that). Anyway, since it is a new app with only screen x, dumping all the tags would then show you the tags used on screen x.