Vim hide lines and unfold them

You can press V to go into Visual Line mode, select the lines to be folded, then "zf" to make a manual fold.

You'll need to :

set foldmethod=manual

if it isn't already set.

"za" to unfold

by folding

https://vim.fandom.com/wiki/Folding#Manual_folding

vim fold manualy some like adhoc vim fold manually some like ad hoc

vim fold selected lines

https://vi.stackexchange.com/questions/3124/fold-selected-lines