Here's a suggestion for note creation and display for various Cartographer note addons. For anyone who has mined or done the Netherwing Dailies you know that some spawn points are underground. By default, Blizzard displays underground items as a dimmed dot on the minimap. A similar thing could be done with the Cartographer notes. There is a variable in WoW that says whether you can mount or not in an area. Generally this variable is false for when you are indoors and true when you are outdoors. I don't know what the variable is, but I'm sure someone has found it.
Here's hoe this would work:
Collection: When adding a note the addon would check indoor or outdoors. The note would then be tagged appropriately.
Viewing: Cartographer would detect whether or not you were indoors or out and display only those notes that were tagged accordingly. Perhaps the tags that are not where the player is (inside/outside) could be dimmed (like Blizz's default tracker) or just not displayed at all.
I would work on the code myself except I'm terrible with coding, but hopefully someone can figure this out.