Hi Matt,
Thank you very much for your insights and guidance.
I just want to provide more details of the setup which works for me (in the case where there are people wondering)
First, I override the fixed with of the left dock (e.g., light.css)
.docked-view-left { width: auto !important; }
Secondly, I need to add 'minWidth' property to the view configured for the left dock.
Thirdly, to expand/collapse the left dock, I need to change the 'minWidth' accordingly (e.g., using messages in Perspective)
