Is there a way to know which themes have been used? For example, if I purchased 10 themes and have only used 2 - how can I tell which ones have not been used?
Alternatively, is there a way to take the license key from a website and know which download it goes to? I want to know this so I can download the right theme files for that client.
There is no such features and you have to make your own note for this. some author provide their own support forum where a feature exist to see your used licenses and domains list.