Binder to show only a sub-folder, with hierarchy

Hi, apologies in advance, this should be straightforward. I had a setup that I liked, but I cannot find my way back to it and I am probably searching with the wrong terms.

I would like the binder to only show a single folder of my project, with the hierarchy still there.

I have tried my way around collections, but that seems to not do the job, as the hierarchy seems to get lost.

Can anyone advise? Many thanks!!

Hoisting the Binder

Page 109 of the Manual. Section 6.3

Not quite the term I was googling, but this is exactly it.