I wonder, why the skeletal mesh editor does highlight bones in a somewhat confusing way. I selected the weight display to clarify, what I mean:
Here, you can see, while the lower arm bone is selected and weights are correctly shown, the actual highlighted Bone visually is the bone one level above, here, the upper arm.
Things are working, no problems, but if I create models in blender, the bones themselves are displayed in a much more intuitive way. I just wonder, why the highlight is done from the bone rotation point backwards in UE4.