“Saddle N” means “Tap any number of other untapped creatures you control with total power N or greater: This permanent becomes saddled until end of turn. Activate only as a sorcery.”

You may activate a permanent’s saddle ability even if that permanent is already saddled.

“Saddled” isn’t an ability that a creature has. It’s just something true about that creature. It won’t stop being saddled until the turn ends or it leaves the battlefield.

Creatures with saddle can attack or block as normal even if they aren’t saddled.

In the rare case where +1/+1 counters can’t be put on one or more creatures you control, you still gain 1 life for each creature you control when Bounding Felidar’s first ability resolves.

If a permanent becomes a copy of a saddled Mount, the copy won’t be saddled.

An ability that triggers when a creature “attacks while saddled” will trigger only if that creature was saddled when it was declared as an attacker.