Essentially I’d like to separate out a list of data based on true/falses, then do some sort of operation on those separately, and finally re-combining all the items back together retaining their original indices.
Is this just an example of a more complex issue?
Only this situation can be done with a simple Code Block:
nr <= 50 ? nr/100 : nr;
If you don’t mind the warning from processing a null value, you can also split the list in two replacing opposing conditions with null by using something like this:
passingSetAndNulls = test? value: null;
!failingSetAndNulls = test? value: null;