There used to be an addon, "Open tabs from clipboard URLs" but I can't seem to find it anymore.

The best I find now is, an addon that opens a box, then you paste your URLs in it, then you press a button.

That's not what I want. I want a toolbar button, I press it, the tabs open.

So that I can opens large blocks of URLs.

Also, I would like another addon which opens large blocks of URLs but does not load them immediately.

I have LoadOnSelect3 for this, but the problem with that one, is that it opens special moz:// pages until you load the tab. And that breaks searching and filtering tabs because the tab title and URL are not the real ones.