(Note, the screenshots in this idea are from the Sören Hentzschel article giving a first look at the Firefox "Nova" redesign. They are not officially featured by Mozilla. Development on Nova is still early and things may change from the posting of this idea)
Mozilla is currently working on a Firefox UI redesign, internally named "Nova". Nova features a rounded appearance where elements are nested inside floating island UI elements.
Firefox Nova Redesign Screenshot
I have a couple of concerns with the current redesign stemming from the space between islands attached to the main content area. They are are:
A potential solution would be to allow the space between islands to be collapsed. I have included a mockup demonstrating what a collapsed version could look like:
It is possible that these issues may be solved in the future with a custom userChrome.css, but since there is currently no public release with the Nova redesign I cannot say how feasible that is. Because of how core islands appear to look to the Nova redesign I am worried that approach may be more difficult than usual.