Stepway happy to help you but then idea of concatenating multiple fields, also acting as list fields and only then using this for further manipulation or testing seems unnecessarily complex.
perhaps if we know the larger problem we can give you a better solution?
Have you tried the filter run prefix intersection?
The first part of the problem is to combine contents of multiple fields into a variable, e.g., concat.list that can then be used in the intersection.
The works if I use literal strings for concat.list and the target list. When I use a function to do the concatenation it fails. What is most confusing is that the two input string look identical.
I am having difficulty in explaining what I am trying to do. This suggests that my approach is probably not well thought out. I will post again once I have a coherent description.
I forget to add that the json code, breakout of the filter into three parts and links to documentation
in your reply made your solution easy to understand and adapt. Thanks again