Hi Zoombapup,
I just wanted to clarify a couple of things before offering my answer or assistance.
Are you only asking about adjusting the new collision feature in the mesh editor/viewer? I’m able to select any type of collision I’ve created and use the Rotation, Scale, and Placement modes.
I made something similar with multiple boxes like the image below to indicate
Again, just to be clear, this has nothing to do with blueprints or adjusting collision scale at run-time but just applying collision in the editor using the collision tools that are now available in 4.3, right?
Let me know, as I’m not seeing this issue with that but that doesn’t mean there’s not an issue that we can look into. 
Tim