This feature is partially - but not fully - keyboard drivable. Please add:

• Please add keyboard command to collapse current island, if currently selected tab is part of an island.
• When using keyboard to "Show Previous Tab" or "Show Next Tab", collapsed tab islands are skipped over. They should not be skipped; rather, they should get the keyboard focus. At that point, there should be a keyboard command to expand currently selected (collapsed) island.
  Tab Islands is a nice feature for mouse-centric casual users. Great! The mouse works.
  Tab Islands is also a nice feature for keyboard-centric organized users. Great! Well...... not quite there yet.
  TL;DR: Add full keyboard drivability.
  Thanks!