In vertical Tabs, most Tabs don’t have a close Button, only the active and hovered Tabs do.
So if the Favicons stay on the left, the left‑aligned close Button would either have to replace the Favicon, or displace the Favicon and Tab Title towards the right; both Designs could be disorienting.
A third Option could be to place the Favicon to the right, so the left‑aligned close Button would not need to disrupt the Layout in any of these Ways, only the Tab Title would need to move silghtly. It also avoids the Favicons moving much when expanding or collapsing the right‑sided Tabs. But moving the Tab Title could still be disorienting. So there should be a Margin to the left, just big enough so close Buttons can appear there without displacing anything.
But that Design separates left‑aligned Tab Titles from their right‑aligned Favicons, if the Tab Titles are short enough. The Solution for that is to add a faint horizontal Line between the Tab Title and the Favicon:
Example Domain ——— ■
