New tab button is far right rather than next to the last tab

[Charpetlol]

Before reporting your issue

• My version of Firefox is up to date (for 115, this means being on at least 115.16.1)
• My copy of Geckium is up to date (no update option in the hamburger/spanner menu)
• I deleted the entire "chrome" folder from my Firefox Profile, if there was one, before installing Geckium

What browser are you running Geckium on?

Eclipse r3dfox

What Operating System are you running Geckium on?

Windows 8.1

Summarise the issue

The new tab button is at the far right rather than next to the last tab. This can easily be fixed by removing the tab button and adding it back via Customize Toolbar..., but it's still a weird bug

Screenshots

How do you reproduce the bug/inaccuracy?

1. Open r3dfox after a restart or two. That's it.

Expected behaviour or design

Of course, I expected the new tab button to be right next to the last tab

Additional Context

No response