Simply right clicking on the video brought up the option to copy the video URL at the current time, but left clicking the option did not work. (I’m using Firefox)
So I right clicked on the option, which brought up another menu. This menu had the option to google search for the URL, which turned out to be the correct one.
EDIT: I just found out that maybe it did sort of work the normal way. Because now I saw that my youtube post had the URL several times. So maybe the previous times I tried to paste the URL did work, but it was simply invisible until I submitted the post? I’m not sure.