Obsidian's Outliner plugin provides a Workflowy-equivalent UX (as a complement to Obsidian's great UX and massive featureset).

Used WorkFlowy for about 7 years, dropped it when I got tired of the lack of feature updates, no end-to-end encryption and only Dropbox for automatic backups.

Workflowy is quite nice, but I do worry about it being online unencrypted.