Is there a way to make subpages?

I’m trying to make a collection of posts that don’t show up in my feed of normal posts. Essential it’s a book notes collection which is different from my ordinary blog posts. Is there a way to make sub pages that could be embedded in another page rather than using a tag?

You could probably change the filter of the default page / and use that to include all tags, minus the ones you care about. Then your homepage is filtered of them by default and would allow tag system to be used for sub-pages.

See Ghost Themes - Dynamic URLs & Routing & Tutorial: Building content collections with Ghost

Thanks, how would I change the default page filter?

You add a filter tag to the / collection in the routes.yaml file.