It only copies that tabs of the particular window you are in. I have over 15 windows open. I will need to repeat this action 15 times. Very impractical.

Additionally, it does not leave any space between URLs and I'm having trouble figuring out where each one ends.

A little better design, like having an empty line between them, would have solved this problem.

To sad they didn't do these two points.
I'm going to remove it.

I would love to use this, but clicking the button does not copy anything to my clipboard, and the author has provided no means of contact or bug reporting.