Just make a star that allows you to see that you bookmarked a replay in the replay list. That would be good enough, but aditional tab for bookmarked replays would even be better.
Maybe you can even add a “note” to it somehow, so you don’t forget.
This is useful for remembering cool replays, saving replays for youtube or for coachings (so you know which replay to show to a coach)
Maybe also add “tags” to replays. So they could be seen and also searched through tags. Not really necessary though