For my first Inform 7 game I came up with this structure for my code.
I used Volumes to indicate major areas.
I used Books to indicate individual settings, characters, things, and scenes
I used Parts for specific rooms, characters, things (whole outline not shown)
This structure has evolved over time as The Time Machine source code has grown—v1.0 was written for ParserComp 2021 and I am currently on v1.7 working towards a v2.0 release later this year.