So far a previous map request could be chosen for re-render, but only with the very same settings as originally chosen.
Now there’s finally a “Reedit” button along with the “Recreate” one, allowing you to chose an existing map and then going through the edit dialogs with the original choices being pre-selected, but changeable.
Disclaimer: this is still work in progress, it works well for geographic area selection, but there is only limited support for maps based on a chosen administrative area, and any uploaded files will no longer be present.