Based on my usage experience, I advise that the close button for each tab should be placed in front of each tab when Vertical tabs layout collapsed, then I can close the tab by moving the cursor on the X icon of each tab and then close the tab directly by click even without expanding the Vertical tabs bar. Or the Vertical tabs bar expanded with the close button in front of each tab, so I still don't need to move the cursor a long distance to aim at the close button icon on the right side of each tab. ( Floating the close button in the top-left corner of each tab is worth considering )
But now:
Each time when I close a tab, I need to repeat the procedures again and again !!