It would be pretty awesome if there was a repertoire feature on lichess. The idea is that you can make an opening book or tree that you can edit and change to fit the openings that you use or play against. Either it could be one big repertoire, or two repertoires; one for white, the other for black. For example, I play the Sicilian, so in the Repertoire for black, I could include the Sicilian but I don't need to put the French in there sine I don't play it. Another cool feature for this would be for the computer giving you a position from your repertoire and it working like the old opening explorer. Hope you consider this idea!