Is Drafts the only destination for the reminders you are creating? I am simply wondering if asking Siri to create a new draft might suffice, and what the reason to import from multiple reminders lists would be.
The existing scripting options for reminders looks like it would support creating an action to import from multiple lists if you did want to go down that route. You would need to know what lists you want to import from, if not simply all, any match criteria (e.g., incomplete tasks only), what you want to do to the reminder after import, etc.