FoldingText for Atom is a work in progress. Right now my focus is on incorporating feedback and getting it stable for a 1.0 release.
Once that's done I expect:
I'll add support for reading/writing/editing other file formats. In particular OPML, TaskPaper, and Markdown (ordered by ease if implementation).
I'll built a standalone version so that people can use "FoldingText" without needing to intall or use the rest of Atom.