This is nice vim emulation, but why not take notes in vim in the same way? It can do all the same stuff and you don't need to leave the editor. vimwiki is never more than three keystrokes away...
- Instantly collapsable/expandable lists (I guess maybe vim folds by indentation could be used?)
- Open sub-list in new window
- Mark a "task" as done
- Basic text formatting (italics/strikethrough/monospace)
- Easy way to "search everything, show a list of results, jump to the context of the chosen result".
In contrast, vimflowy makes all of these quite easy and intuitive.
Yes, `set foldmethod=indent`
> - Open sub-list in new window
This is something I'm not sure exists as a ready-made solution, you'll have to write a function for that. It's trivial for the majority of cases though.
> - Mark a "task" as done
> - Basic text formatting (italics/strikethrough/monospace)
I use vimwiki that has this, there are a lot of other ways to achieve the same.
> - Easy way to "search everything, show a list of results, jump to the context of the chosen result"
fzf.vim. The above and also supports fuzzy search.
> This is something I'm not sure exists as a ready-made solution, you'll have to write a function for that. It's trivial for the majority of cases though.
gf (or <Ctrl+W>f for the new window version) could be useful for this, if the sublists are separate files: https://vim.fandom.com/wiki/Open_file_under_cursor
For a Linux user, you can already build such a system yourself quite trivially by getting an FTP account, mounting it locally with curlftpfs, and then using SVN or CVS on the mounted filesystem. From Windows or Mac, this FTP account could be accessed through built-in software.