Clipping Layers Appearance Option (Opposite of Masking)
The introduction of the "Masking Layers" option under the layer appearance tab has been a major improvement for creating custom cartography. It however, falls short by not having the ability to accomplish the opposite at a layer level. There needs to be a "Clipping" layer option that functions exactly the same as Masking with the opposite results.
The "Clip Layer" option under Map Properties is very limited and doesn't give you the same flexibility needed. With it, you can only define 1 outline to use for the entire map. This doesn't provide the same layer by layer customization found using the masking option.
Basic Example: I have a building layer that I want to display differently for buildings inside city limits vs outside. The building layer doesn't have any attributes to quickly query on. I can easily separate and symbolize the buildings outside city limits by masking them using the city polygon. However, to quickly separate the buildings inside would require an opposite polygon of the city limits to use as a mask, using the clipping tool to create a new dataset, add attributes to the building features, using the map level clip layers which wouldn't allow for any other customization on other layers, etc. And, yes there are many other work arounds that I'm aware of, so I'm not looking for suggestions because in the end none would be as quick and easy as using the same layer I used for masking but to clip.
Another example would be to mask and clip road lines to display the labels differently inside and outside a boundary.