When checked (the default), submitted values must match one of the entries returned by the REST endpoint and the build form renders a strict dropdown.

Uncheck it to render a free-text input backed by a datalist of the fetched values: the user can still pick a suggestion, but is also allowed to type or paste any value, and the build will not reject it. This is a partial workaround for paginated REST APIs whose desired value falls outside the first page returned to the plugin (see #61 and #86).