We already have large sets of actions in some Action bars. The design concept behind Action bars actually also asks for sections, not only groups (we already group actions). Sections bundle related actions under a title and can be opened and closed.

The design ideas behind sections are:

• Sections bundle related actions under a common topic (e.g. "Personalization", "Versions")
• By default, only the first (primary) section is open, all others are closed. In addition, you can configure a particular section to be also always open by default.
• On mobile devices, mainly the primary section is available. Optionally, a second section can be made available as well. Sections don't show their titles, though.
• In the secondary menu opened on right-mouse click, only the primary section is available.

Having a clear distinction between the primary and other sections requires developers and designers to decide on the core set of actions they want to offer in any given app or sub app. It also helps in keeping a low UI complexity in cases there's not a lot of space for showing actions.

As for the current state of implementation, we already do have limited support for sections. We can configure them, but not open and close them. In addition, action availability is not aware of sections.