> Fish also uses threads for its award-winning (note to editor: find an actual award) autosuggestions and syntax highlighting, and one long-term project is to add concurrency to the language.
The two most popular zsh plugins are total clones of this at 31k and 20k gh stars respectively. Not an award but certainly an indication of its success.
Having used zsh with those plugins for a while and not having used fish personally, I'll nominate them for "most desirable plugins to copy for your own shell to make it more user-friendly".
(note to editor: find an actual award)