You will be happy to see that the feature you are requesting is implemented in 0.11.0 according to thread in this link here: Remembering heading and indent collapse in notes
However, this thread is about being able to quickly fold and unfold to a certain level. It is also a thread where some people’s requests for additional types of hot keys as they relate to folding have been merged. See here: Fold/Unfold headings up to specific level hotkeys - #12 by I-d-as . I make this distinction to avoid this thread being closed with this newly implemented feature that you are requesting.
I hope this is not interpreted that I am expecting this to be closed or that I am annoyed my request was merged here. I am just making it clear. I think the moderators do an excellent job on this forum and very much appreciate them!
Thanks.