Do these functions exist, or can I suggest them please.

There are two things here. Can somebody please tell me if these functions already exist, and if it just the case that I can't find them....or, if they do not exist, can I suggest them please.

First: 'Add game to library' function. There are some games that, for whatever reason (maybe I want to study a mistake in more detail, or explore a line in more detail) I'd like to save to a library of my games. Does this function already exist?

Secondly: 'Search by centipawn loss' function. I was idly searching, and wondered what is the 'best' game I have played in terms of fewest inaccuracies, mistakes, blunders, but couldn't find a way to do that in advanced search options. Is there such a way?

If not, can I suggest both, especially the first option. I think a library of games that a player wants to revisit for whatever reason might be useful.

Thanks.

just create a study with the game you want..

"First: 'Add game to library' function. There are some games that, for whatever reason (maybe I want to study a mistake in more detail, or explore a line in more detail) I'd like to save to a library of my games. Does this function already exist?"

As far as I know you can bookmark a game. See this link. I have added some screenshot

pasteboard.co/I1S2hl9.png

@stam_mathematician

Thanks, that's great, never knew about that, and it's basically what I'm looking for.

@theosarugambit Regarding your second question, it is not possible to sort the games by average centipawn loss.

There was already a discussion on the exact matter on January 3, 2019. Here is the link of the discussion lichess.org/forum/lichess-feedback/find-games-based-on-centipawn-loss

Presently these search filters are available. lichess.org/@/theosarugambit/search
Thanks and have a nice day.

CPL is mostly meaningless. There are games with low CPL just cause there were lots of moves in the endgame with dead 0 evaluation. It doesn't mean that players played strongly, but that the position was simple enough. Works the same way in the middlegame.