As an additional thought, you may want to ditch the traditional save function for one that uses recorded tables to take down inventory and various world and character states. Otherwise, each time you bolt on a new section to your game, it’ll invalidate any existing save files as it will ostensibly be a new game file. If you would like previous players to continue playing with each new installment, forcing them to repeat their previous progress each time would probably be discouraging. I believe @Afterward did something similar to that in Ryan Veeder’s Authentic Fly Fishing, but I’d be fine with being corrected if I’m wrong.
ETA: I found the post where Veeder spells out how it is done. Might be useful: The Imitable Process of Ryan Veeder: Autosaving in Inform 7