Explain the problem as you see it
There are only "CHILD OF", "LINKS TO" and "OWNED BY" search operators that somewhat relates to parent/child/descendant relationship. There is no way however to search through all descendants of a given node, i.e. through deeper levels than "CHILD OF" can search.
Why is this a problem for you?
I am not able to create powerful searches like extracting all sources from text based on multiple quotes, each with its own source.
Suggest a solution
"DESCENDANTS OF" search operator.