Sometimes I need to generate a custom order for paper, in particular when prioritizing readings. Do you plan to implement that in the future?
I’m not sure how this would work. It would require defining a custom field that is sortable. The closest that would come to my mind is a “rating” field, which some programs have. We don’t have plans going into this direction though.
A simple workaround would be to define multiple labels, e.g. “must read”, “read later”, “maybe sometimes”. That would be the same as defining a score 1,2,3.
See also @Kerim’s nice tip here: Tip: use unicode ★ character to add ratings