TaskPaper is a Mac app for task management. It appears to be an attempt to make a Mac-friendly replication of the essential bits of Org-mode that doesn't rely on Emacs. However, "essential" is subjective.
On https://margin.love/#/ , Alex Gamburg sells a new format (Margin) that attempts to provide a more general-purpose format than TaskPaper's text format. Gamburg appears to be frustrated with lack of specification of the TaskPaper format, and how TaskPaper is overly-opinionated about structure. In particular, "TaskPaper splits items into
notes" whereas Margin just has "items". Additionally, Margin seems to allow a lot of flexibility in the formatting of the text.