Since the global line feature was enabled, removing a line is different for me. I noted this in my video, but I found that you have to first select the line and then you can remove it. So I left click the line and it will give me those little boxes on the ends. Then I right click and remove the line.
If you haven’t tried that, give it a shot.
I have marked the video to start directly at the spot where I reference it. You’ll see when I left click the line, the little boxes on the ends of the line appear. That shows the line has been selected. Then I right click and choose remove