Meaning that whenever you enter a specific mount your character itself would be hidden.
The character mesh has an ‘Is visible’ flag that you should be able to flip using a blueprint graph. I’m not sure where you would have to build it, but I suspect it would work best as part of the saddle.
Yup, can confirm Blue is on the right track with this one. Use an Event on Overlap or something else that you find will be suitable for the task, and have it trigger bIsVisible (IsVisible) when the CharacterPawn is overlapping the saddle I believe. You might have to mess around with adding another invisible component to the saddle to get it working 100% as intended. That should work in theory.