When using the save render elements button (S),
it saves the selected passes elements.
When loading, the list on the left shows the
pass names in the saved data, and if you expand each you can see
the elements that were saved for each pass - you cannot load just
part of a passes elements.
Loading elements into a pass does not replace
the existing elements, it appends the elements - so delete them
first if you want to replace the elements assigned to a pass.
The interface is drag and drop from the left
region to the right to map data in the saved file to data in the