Option to save a moment of a game

That could be done with the Library feature.
https://support.chess.com/en/articles/8609806-how-do-i-use-the-chess-com-library
Ref reply#2 : Thanks. But library option saves whole game. If we wish to bookmark/save a particular moment from a game, how to do that?

Ref reply#2 : Thanks. But library option saves whole game. If we wish to bookmark/save a particular moment from a game, how to do that?
You could open in an analysis board and strip out moves to keep only the ones your interested in and then add it to a Library collection
https://support.chess.com/en/articles/8583825-how-do-i-use-the-analysis-board
If you just want a singular position, you can look at that position, use the share option to grab the FEN, and load that directly.