As far as I know, once you delete them from your queue, they switch to your history and automatically get deleted. If you reactivate them back from the history list, they are downloaded again. So, in the first place, this should be no problem.

Then there are three ways to see wether you once STARTED a map or not.

First, it's greyed out in your queue list.

Or, when deleted from that list, the already mentioned "my history" list shows the chambers you started at least (not sure if it contains EVERYTHING you ever started)

Plus, in the workshop's thumbnail preview of subscribable chambers you can see a mouse symbol that tells you it has already been started at some point.

There's noting that tells you if the chamber has been FINISHED.
Nothing but your rating eventually (depends on you).

Hope this helped.

Originally posted by SpielSatzFail:

Plus, in the workshop's thumbnail preview of subscribable chambers you can see a mouse symbol that tells you it has already been started at some point.

it helps a lot. i'm sure every chamber i'd started had been finished. so no more problem. thank you.

I found another easy way to see all the chambers :-)
Steam homepage -> Portal 2's Workshop page -> search -> played (last in the drop down menu).
Or similar, mine is in german and I can just guess what exactly it's called in englisch.

So to say right above this conversation and below the Portal 2 brand, going one step to the left :-)

Originally posted by SpielSatzFail:

I found another easy way to see all the chambers :-)
Steam homepage -> Portal 2's Workshop page -> search -> played (last in the drop down menu).
Or similar, mine is in german and I can just guess what it's called exactly in englisch.

So to say right above this conversation and below the Portal 2 brand, going one step to the left :-)