Explain the problem as you see it
When viewing a list of lists, I usually "expand all" children of a certain node, read the children and their children, and in the end I want to collapse it all again, to remove visual clutter and get to the next parent node which I want to expand all, read, collapse all.
Currently for this I have to scroll up all the way to the expanded parent node and collapse it.
Why is this a problem for you?
Friction, takes time, unnecessary because fixable via this solution.
Suggest a solution
Executing command "Collapse All" on an already collapsed node (in this case a child node of the parent node I want to re-collapse) should collapse the parent node instead of doing nothing as is currently the case.