In a sane world, selection of steady versus dynamic flying would be a toggle on a per-mount basis. But this is not a sane world.
Does the macro system (or the scripting engine underneath) give access to controlling the flying mode toggle to allow me to create a mount macro for specific mounts that will always use a designated flying mode for a particular mount? For instance, always steady flying for mounts with aquatic capability, to prevent losing the swim speed bonus just because the current overall toggle is dynamic flying.