Perfect. Exactly what I was looking for. I wanted a nice lightweight extension that would give me the option of opening a tab next to the current tab, while preferably still allowing the default behavior of tab at end in other circumstances. This extension does exactly that, and it does it perfectly.

I understand the new Mozilla restrictions in that the added context menu items can't be inserted within the current menu, only at the bottom, and I appreciate that the dev still put it on there. Thanks again for providing exactly what I was looking for. 8-)