Update: The RTK 6th Edition Support development is put on hold indefinitely, due to lack of feedback on this feature. I posted a prototype for a new lessons page on the forum, hoping that would generate some ideas.

RTK 6th Edition Users: All the 6th edition characters are available in the Study pages and the keywords are mostly identical, however the frame numbers (the index) is different. To add flashcards with the 6th edition index, have a look at the 6th Edition Frame Number Converter kindly shared by gomtuu on the forums.