Hiding Content Types from the Studio Menu

Is it possible to control what is visible under "Content" all the way on the left side in the studio? Specifically, I'd like to hide some content types from this list - some types only make sense embedded in other objects.

You can use "object" instead of "document" as the type to achieve this.

Structure builder is your friend https://www.sanity.io/docs/overview-structure-builder

The example here would be close to something you would need https://www.sanity.io/docs/structure-builder-typical-use-cases#adding-additional-site-settings-documents-cc0a0be8c837

object vs document was just what I was looking for, thanks!

Ah, in my haste I overlooked your last sentence 😄