Trevor says this requires re-writing toolbars to separate the Model from the View. His comment on proposed code design is appreciated. :-)

This would allow:

• a bar with direct items and a sub-group shown as a list
• a list with direct items and a sub-group shown as a bar of obvious buttons
• a list with direct items and a sub-group shown as a sub-list
• a menu with a text-box for entry of a value (e.g. Google Doc's "help" menu)
• a menu with multiple sub-groups split by a horizontal bar – bug 71616 for this

… and other things, no doubt.

Version: unspecified
Severity: enhancement