This is visible only when an object with fill is selected.
About organizing layers: there are two features (one already existed with a minor bug).
The first (new) feature is the "Place Before/After/Inside" commands from the Layers panel menu.

assuming that the on canvas and Layers panel selection are not synchronized (here is the advantage)
select some objects on the canvas (with the regular selection tools).
scroll to and highlight an object in the Layers panel (this will have the strong blue highlight).
then the "Place Before/After/Inside" commands of the Layers panel menu will place the selection on the canvas before/after/inside the highlighted object.

The other (existing) feature is using multiple Layers panels. In the Layers panel menu use the "Open New Panel" command to open another layers panel. Now you can position each list differently and use drag & drop to move or copy objects between the panels.
There are also the "Open with..." layer panel opening modes that will fix the opened panel content to the current document (or location) and can be used to copy objects into (or from) an other document.

Sidetrack this topic

Transformed Fill, found it!

Organizing layers
Without making it more difficult with multi layer panels, my point in the aforementioned post was moving objects with layers in closed state. The mentioned functionalities do not solved this. Or am I not seeing that correctly?