Is there a way to mark/label a special use switch?
Use a timer switch for the switched receptacle. You can get a two gang face plate that has one standard 15A switch opening next to a decora (square) opening. That's a very common configuration for a powder room, where you usually see one single pole switch next to a GFCI receptacle.

The switch I linked to is just an example. You can get one that has typical on/off functionality as well as timer functionality.

This adds convenience, as you don't have to remember to turn it on (and off) manually, and makes it obvious that the second switch controls something else. You can then label it too, if you like.

I believe Leviton makes a nice programmable timer that has a button on the bottom for an override (always on / off), which is probably what you want. Any local DIY supply house or electrical supply shop will have several.