Webflow Logic + Mailchimp (Tags and Update)

I used this guide to set up a workflow using Mailchimp: Add Mailchimp subscribers with Logic | Webflow University

But I ran into an issue where it won’t let me update subscribers, only add them. Updating requires the use of a PUT request. I’ve tried modifying the body of the message, but I can’t get it to work. The PUT documentation is here: https://mailchimp.com/developer/marketing/api/list-merges/

Any suggestions on how I can make this work? Ideally I can append tags as well.