Nobody starts from zero — the thesis draft is in Word, the novel is in Scrivener, the notes are already Markdown. All three roads lead in, and because a Folio project is plain files, none of them is a leap of faith.
Word (.docx) import (Pro) converts the document to clean Markdown in your binder: headings, emphasis, lists, tables, and footnotes carry over, and embedded images are extracted into the Research folder as real files, re-linked from the text. From there, split the wall of text into binder-sized sections (the compile reassembles them in order).
Got a .docx full of a co-author's tracked changes instead? That's not an import job — Import Review turns it into proposals you accept or reject.
There's no one-click .scriv importer — Scrivener's format is a package of RTF — but the road is short: in Scrivener, compile/export to Word or to plain text with Markdown, then import (or drop) the result. Rebuild the binder by splitting into sections; your corkboard synopses are worth carrying over by hand into each new document's synopsis field. Most projects move in an afternoon.
The best case: a Folio project is a folder, so existing .md files can be dropped straight in and appear in the binder. Obsidian notes, pandoc manuscripts, old blog drafts — no conversion, because there's nothing to convert. Your .bib comes along the same way: drop it in the Bibliography folder and citations resolve.
Three finishing touches: set section types and statuses in the outline, attach or merge your bibliography (Zotero guide), and run a first compile to see the typeset result — the 10-minute setup covers that loop.