Relative and Absolute are the same in this case, because the parent of the cylinder is the root component of the actor, and I did not rotate the actor in the scene.
My bad, I should have thought about this.
So here I added X=90° to the placed actor in scene, now the actor is horizontal by default :
AddLocalRotation rotates around the cylinder’s local Z axis
AddRelativeRotation rotates around the cylinder parent’s local Z axis (= root component in this case)
AddAbsoluteRotation rotates around the world’s Z axis
