• Copy Other Array
The array itself becomes a copy of the another array you selected
• Add Array Index
Set the value into the child entry you defined
• Define Manually
Set the value into the child or grandchild entry you defined more freely
"Add Array Index" and "Define Manually" are virtually the same thing for one-dimensional arrays. "Define Manually" allows to dynamically create or replace or make changes to any of entries, including multi-dimensional ones.