Since the launch of patch 8.0, I've reset my UI and mods and have become a little obsessed with pairing down the number of buttons I have on-screen. Here's a macro I'm using for my mounts; it lets you switch between a flying and ground mount, plus a utility/vendor mount, and another for use in water:
/use [mod:shift] Primal Flamesaber
/use [mod:ctrl] Traveler's Tundra Mammoth
/use [mod:alt] Brinedeep Bottom-Feeder
/use [nomod] Archmage's Prismatic Disc
I know it's possible to trigger a mount based on whether flying is enabled in the current zone by using the
[noflyable] tags, but I wanted the extra control of being able to choose specifically.