When I have a Project open in ArcGIS Pro, I can see the individual layers within each given Map in the Catalog window. However, even though I can* preview a given layer in Catalog, I need to completely open the Map in order to copy a layer and paste it into another Map (e.g. to mess around with it in a less cluttered workspace while I tweak symbology or something).
Often I have ~50 moderately complicated layers in the "master" map and it can be time consuming for it to open and render that -- just to be able to right-click a layer, select Copy, and close the map back out.
It would be convenient to be able to copy layers from one Map to another within Pro Catalog without needing to open the source Map (and potentially be able to paste without opening the destination Map!). For bonus points, I would also like to be able to take layers out of a Map in that Catalog space. I can copy or delete a symbol out of a Style file in the Project Catalog...
* I can allegedly preview layers... Even though that option is there, it always says "this item cannot be previewed" when I select it.