Currently you have keyboard shortcuts to go to the next and previous tabs on the tab bar: Ctrl-Tab and Ctrl-Shift-Tab, or Ctrl-PgUp and Ctrl-PgDn
A keyboard shortcut to switch to the previous tab you were on would be very useful. This is possible in Firefox although not in Chrome (without a plugin).
You can use Ctrl-Tab and Ctrl-Shift-Tab for MRU order (like in Firefox) because you already have Ctrl-PgUp and Ctrl-PgDn for directional order.
Or, since PgUp and PgDn aren’t available on laptop keyboards, add Ctrl-Shift-⬅️ and Ctrl-Shift-➡️. Or add Ctrl-Alt-Tab as a “previous tab” shortcut.
(By Ctrl above I mean the Mac tertiary modifier key, not the Windows primary modifier key)