I’m assuming you have to actually put what mount you want summoned
When they made dragon riding available everywhere it messed with the mount macros, so I created one with modifiers, here is what I’m using:
#showtooltip
/use [mod:alt]Grand Expedition Yak;[mod:shift]Renewed Proto-Drake;[mod:ctrl]Traveler’s Tundra Mammoth;[indoors]Carcinized Zerethsteed;[outdoors]Headless Horseman’s Mount
/dismount [mounted]
That last mount will be your default when outside, so you can swap things around based on what you want to use modifier keys for. You can eliminate the ‘indoors’ portion, I just like a different mount inside instances that have areas you can mount.