I am aware of the reference viewer, but I want to edit this tree. How can I do this? Thanks in advance.
I think you got a wrong understanding of that the reference viewer does.
You can not edit it “directly”. It just shows you the current references of the asset and what assets it is currently referenced by. To “edit” the reference tree you have to edit the blueprint itself to refence or not reference the assets. References can be at a lot of locations in the blueprint for example in the default values, the components or in the graph.
Hope this clears things up.