Paste config in any of the three formats. It's auto-detected and converted to the other two, live, as you type.
The converter looks at the shape of what you pasted: text starting with { or [ is treated as JSON, text with [section] headers or flat key = value lines is treated as TOML, and anything else — indentation-based key: value — is treated as YAML. You can always check which one it picked in the status line under the editor.
YAML parsing uses js-yaml, a complete YAML 1.2 implementation, so anchors, multi-document files, and complex nesting all work correctly. TOML support is a hand-written parser covering the common subset: key/value pairs, [table] and [table.sub] headers, strings, numbers, booleans, and flat arrays. Array-of-tables ([[x]]) and multiline strings aren't supported yet.