I think it would be interesting being able to open new tabs in inverse order. I mean:
1) When using horizontal tabs:
- Show the "Open a new tab" icon at the left of the opened tabs
- Open the new tabs (when clicking that icon) at the left of the rest of the opened tabs
2) When using vertical tabs:
- Show the "New tab" element above the opened tabs
- Open the new tabs (when clicking that element) above of the rest of the opened tabs