Hiya! flowchart.png is just inside the folder for the game (note, not inside the folder called "game").
If you're missing it, you may have downloaded an earlier version that didn't include it in the folder... I hope not, because the way I coded it in the earlier version made completing the game a pain... Basically, the endings you got didn't get saved if you reloaded from an earlier save instead of just jumping to a new timeline. If that's the case, I recommend just going back and using F.Skip to get those flags again, and avoiding reloading from earlier saves. Sorry about that! ;;;;