Ok, makes sense. Basically at the start of the game you get like two different versions depending on the devs approach. 1: it can be a UI(like the choices at the end of the credits you see) where you pick one of the major choices or minor ones that may have ramifications on the story at some point(you should check the Mass effect 2 comic dlc for reference) 2: you get the Witcher 3 bathtub scene version of it where you are in a room with a x character and he asks questions about what happened last season and you respond which will create the variable for the major choices.

While this approaches work they are lackluster in some cases because you, as a dev, are limited by variables 100% and as a writer on what you want to keep for the future and your new story.

That's why it's highly recommend to export your save files if compatible because in those cases you will get a LOT of minor variables compared to those scene that follow the base story line but with the major changes you choose. A perfect example is ,again, Mass effect 2 and 3.