[Dynamic Pages] How do I use external collection fields as path parameters?

I have an external collection and I’d like to use one of the fields as part of the page url in order to filter elements. However, it seems that the only field I can use is the ID field, it won’t let me use any other.


In the image above, the error message makes it seem like the field I’m trying to use is not a string or a number, however, in the image below we can see that it is in-fact text: