Create a Dynamic group based on tags

Is there a way to create a Dynamic group based on asset tags?

Yes, in the Asset Group Filter, use
User-added custom tag

I saw that option but we have AWS instances that scale up and down and I want to add those assets to a dynamic group based on tags discovered by Rapid7.

Do they have set naming conventions in UUID like:
amazon-web-services: igfjc834jsajafl0030fdm , Etc

or are you referring to the tagging schemas brought down via the Built in Connector, if so you would be to do what Brandon Said Above but use a “Contains” reference if possible.