Pinned tabs grouped into a single row with vertical tab bar

Pinned tabs formatted with only favicons and no titles are great at saving some horizontal space in the tab bar. Unfortunately this appears to be wasted when using vertical tabs.

For reference:

• Pinned tabs (1-4) at the top of qutebrowser's vertical tab bar

• Pinned tabs at the top of firefox's Tree Style Tabs (TST) extension

I did notice #2627 and #4419 implies some potentially blocking functionality that has already been implemented, but I didn't find any mention of this issue brought up there or anywhere else. It might just be a smaller use case, but I thought it worth pointing out. It is rather jarring to see how pinned tabs come out this way in vertical tabs.