Thank you, I will ask next questions in the Github discussions.
When it comes to "pointer-events: none", that's brilliant, thank you!
I was using it fix another issue I was having.
I have shapes that look very similar to the question blocks in the above demo. When I selected a shape, the selection block was preventing me from using the left half of the ports to drag a link. I will need to fix this problem in a different way than with using "pointer-events: none" on the ".selection-box". You've helped me a lot, though.