Currently in ArcGIS Desktop 10.2 (ArcMap) under the table of contents you can list by drawing order, source, visibility and selection. I think it would be useful to be able to list by coordinate system.
@RoseF I like this idea quite a lot. It would be much more efficient than what I had in mind. It made me think of another option I would like which would be to disable project on the fly. This would force you to project your data before you could use it. In the old days this was just how it was. Just a simple toggle somewhere on the TOC. Turn it off while your processing local data and turn it back on if you need a web services for instance. I think both ideas would be fairly trivial to implement.
If nothing else, maybe Pro could provide the option to LIST/VIEW THE FILEPATHS to the layers listed under MapProperties-->CoordinateSystem-->Layers-->[CoordinateSystems], rather than just their TOC layer names (which can be duplicates, filepaths cannot, unless layer is loaded more than once)?
If not, I upvote the idea to list/order in TOC by spatial coordinate system. We work with a lot of farm equipment shapefile exports that are often named the same, so seeing 1 "culprit" layer named "Tile Pipe" with an Unknown system isn't particularly helpful when you have 1000+ layers named "Tile Pipe" loaded in the map and you need to merge etc.
Pro's project on the fly is handy but the need to get everything into a common spatial reference system for troubleshooting and pre-geoprocessing/analysis data prep hasn't gone away.
Don't forget you can at least see what layers are flagged as different than the current map coordinate system by (1) opening the Edit tab in Contents view, (2) turning editing on, then (3) grouping the culprit layers and to interrogate them individually one by one, working top to bottom, rather than scrolling through Contents when you have hundreds of layers.
