This would be a mini project overview that would appear in the arrange view. Ableton Live for instance has a miniature overview of whatever is present in a project at the top of its session and arrange view.
It can be very helpful when keeping track of larger projects. At a glance one can see how many tracks are in use and one can even use this mini project view to scroll backwards and forwards through a project.
I think vertical scrolling is also possible.
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