Add new tag to folder in UDT instance

I have a UDT instance that has a folder in its definition. I want to be able to add other types of UDT instances to this folder in run time is it possible?

I have been trying system.tag.configure, but I keep getting

The target path does not have item ‘myNewTagName’ for overrides, and cannot accept children tags.

Another way I could ask this question is how do I represent a list of tags in a tag? I was thinking I could make a folder in a UDT and then add and remove tags as necessary during runtime.