Tag files would be another good one.
Tag files would be another good one.
How to enable it: use "set foldmethod=syntax" (with C++) or "set foldmethod=indent" (with JS, where "syntax" doesn't work for me). Also, I use "set foldminlines=0" so that 1-line paragraphs get closed as well (it looks more consistent).
How to use it: close all folds "zM" (I remember it because the M is shaped like it's all folded on itself). Open all folds "zR". Open one fold "zo", close one fold "zc". Open one fold recursively "zO", close one fold recursively "zC".
By the way, I almost never use manual folds, so "zf" is almost useless to me.
Everyone uses tag files, in some sense, when they use :help :)
So while I agree with you in that they aren't a part of my typical workflow, they are a piece of vim that I'm glad I familiarized myself with.
FWIW, I map <Space> to za, so that I can unfold/refold quickly. I also map - to zx to quickly fold up a file I may have drilled some holes in.