Copy rectangle selection in firefox

If you hold down the CTRL key (or Cmd on a Mac), it lets you make that kind of selection. It doesn't paste into Excel how you'd expect, though, so you'll have to see if that's useful to you.

this extension created by me for this purposes chrome.google.com/webstore/detail/table-range-select-and-co/klojbfbefcejadioohmnkhjmbmecfapg?hl=en