Time panel should show top-level entities below the root path

[teh-cmc]

Currently, the time panel pretends that all entities under the root are actually top-level (presumably to avoid wasting horizontal space).

The problem is that it makes it impossible to A) collapse all entities into a single line and B) do so in a single action (as opposed to N).

This for example is the most collapsed i can make the time panel in the Plots example:

not only is it still 5 rows, which is very annoying, but also it took me 5 "right click > collapse" to get there, one for each top-level entity.