In a tittle's info page when we go to the menu to add it to a custom list, we get a list of our existing lists. 

It would be nice if we could see some indication like a checkmark next to a list's name or maybe display somewhere the names of the lists this title is included to know if we have already added this title to a list and in which ones we have added it. 

Because we might have a lot of lists and tittles and forget in which one it is and need to go search all of them one by one to check if we have indeed added it or not.

6votes