1. I really didn't know that it is impossible to list other fields. For instance, it was logical to me Year field to expect to be a list - it is known and exact data, like languages, right?. So were the Frame Rate - there are only a few of them? Then Channels, even Sampling Rates, etc. On the other hand, I haven't had time to discover what is Quality list field meant for. It's still empty for all of my entries, not a single automated filling of it during scanning files.
2. To be honest, I overlooked the congruence of Original Language and Subtitles fields, and the fact that both of them belong to a list named Languages.
3. The question of possibility to add custom made list fields to Lists - remains.