Nested Spaces

I love the way memex allows me to annotate my thoughts live on media, it is the best way I can imagine right now to capture thoughts.
I'd like to switch from notion almost just for that.

However, after the capturing comes the processing, here I'd like some flexibility:
I'd like to be able to annotate annotations (have thoughts on thoughts), and tag annotations (idea, question, insight...), and most importantly, link them to not only a single space but a hierarchy of subjects, because goals (especially mega-goals) tend to break into smaller and smaller issues and i'd like to keep that hierarchy.