Hey there, @Jori! Thanks for reaching out in community - we definitely want to help!
Hmm, while there isn’t a “Updated Tag” trigger for Shopify, there is an “Update Customer” trigger. You may be able to use this and Filter by Zapier to limit it specifically to tags. As you mentioned though, there isn’t an “Add/Remove to Groups” action for Thinkific. There is an open feature request for this which I’ve added you to. While I don’t have an ETA on when or if this will be implemented, this is the best way to stay informed if anything changes as we'll email at that time.
It may be possible to use the Thinkific API and Webhooks by Zapier if you’re comfortable! Here’s a few resources to get you started if you’d like to give that a shot:
It’s worth mentioning this is considered a slightly more advanced approach so any support will be limited. That said, if you’d rather not fuss you can always look into hiring a Zapier Expert to build this for ya!