Created attachment 154723 [details]
Number overlay on Ubuntu Dock

GNOME Extensions (Dash to Dock, Dash To Panel) has option called "Number overlay".
When you switch to some window on a panel using Super+[0-9] (or Super+Q) a badge with a number over app icon appears.

This feature greatly helps with productivity witch a large number of tasks on a panel. For example if there's only 4-5 apps running/pinned on a panel, for average user it's not a problem to find each number and use shortcut Super+{0-9] . But if there's more (it's a common-case when app windows are ungrouped), IMO, user won't bother to count or them and use aforementioned combination (using instead Alt+Tab, mouse selection on a panel etc).
Number overlay appears with GNOME Extension if user:
1) Switches apps with Super+[0-9]
2) Press special keyboard shortcut for that (Super+Q)
3) selected "Always visible" option (it might conflct with different in

As for design and conflict with different badges (progress bar, notifications, sound), this number overlay could be placed:
- over aforementioned badges (like "Dash to Panel" does). However this one would conflict with "Always visible" option
- on the opposite side of the task-manager element (this might conflict with either "sound" indicator or "notification" badge)

I've attached screenshot of "Number overlay" on Ubuntu Dock ("Dash to Dock" GNOME extension version).