LiveCycle ES Processes Do Not Support Collections of Collections
If you try to add a list to a list in a process, you’ll get unexpected behavior — because it’s not supported. Nor can you add a list to a map, a map to a list, or (you guessed it) a map to a map. If you try to add a collection to another collection, each item in the first collection is added to the second, not the collection itself.
Let's say my process has a list variable called listVar. I use the Set Value service to add some values to it:
/process_data/listVar[1] = "abc"
/process_data/listVar[2] = "xyz"
I then try to add this list to another list, uberListVar:
/process_data/uberListVar[1] = listVar
The first item in uberListVar is “abc”, and the second item is “xyz”.