Doesn't work anymore. It's now useless. With 10 tabs open on my right, it can appear anywhere in there and not on my immediate right.

It looks like developer gave up on it since it's been about a year since it's last update.

Doesn't work inside tab groups. :(

Doesn't work when I open link in new tab

Doesn't work at all anymore for years now, so I finally give up.

New tabs are almost never opened right next to the current tab, but ANYWHERE to the right, which means you have to search the new tab AND the old one after stwitching tabs.

That's basically standard FF behavious, so I obviously don't need an addon for that.

Does not work for me. Have only 1 tab open. I have two sites on bookmarks toolbar, which I have set to always show. As soon as I clicked to open one of the two on the bookmarks T.B., it opens on top of active tab. It did not open to the right of the active tab. I also went to about:config, but it was set for 'true.' Perhaps I overlooked something?

doesn't work on my android device!

I think this extension only simplifies the manual inclusion of this option: "browser.tabs.insertAfterCurrent"

This can be done manually using two steps:
1. Type in the address bar: "about:config?filter=browser.tabs.insertAfterCurrent".
2. Set to "true" by double click on it.

Done.