Please note: this Shortcut requires iOS/iPadOS 16 Beta.
This shortcut is currently in beta, also, because the collection-specific portion of its functionality is not working properly. I'm working on troubleshooting it, sorry.
This shortcut uses one of the brand new Safari actions in iOS/iPadOS 16 Beta (
Find Reminders) to retrieve the entirety of one's Safari Reading List as a list of URLs, which it then adds to Raindrop via the Raindrop API.