Where in the Renpy manual is how to do that?
unsure, but I've seen other renpy games allow you to load from specific chapters before you start a game. It offers the option to start at beginning, or chapter 1, or chapter 2 etc.
This way if a player is on the ntr path for example, they don't need to restart a whole game, and cheat menu through every scene in the game to catch up to the update if they wanted to see loyalty path stuff. They could just start a few scenes away from the last update.
I know devs are like, but just use the gallery to see the scenes... it's just that there is a group of players who want to experience scenes within the flow of the game still. Not in the gallery. But without grinding through the WHOLE game.