How do I select middle part of a hyper link?

Try the ToggleLink add-on.

Interestingly, I just found out that pressing Alt allows you to select part of a link with the mouse in Firefox! See if by some chance that works in Chrome as well.

I had the same question, and because there wasn’t a solution for GNU/Linux, I asked the question on Ask Ubuntu.

There, user264504 answered that it’s possible by holding Super + Alt while selecting the text with the mouse.

(As my question was about Firefox and got closed as duplicate for this one, which is about Google Chrome, I think it makes sense to also give solution for Firefox. There is the add-on: Link Toggler.)

If you click right above the link, right when the cursor changes from a hand back to a pointer, and drag across from that point, you can select the middle part of a hyperlink. I just tried it out in Chrome.