Thanks again for joining office hours, @Sharon_Alexander! Lacking a true mutable global variable, I agree with @Shawn_Optipath that coordinating your loop via a JS block is probably the best workaround. While the method that we discussed towards the end of office hours - and described here - does work, you've already noticed that it has some drawbacks.
Let us know if you have any specific questions about implementing something like what's shown above! I'll follow up on the status of the relevant feature request internally. 