I don't understand though. Lets say you're increasing the size of your sprite, you should simply increase the collision shape along with the increased sprite. I am also pretty new but hey, maybe you want to do something cool. As far as I'm concerned I don't think there's any way you can increase size of Kinematic body, after all it requires a sprite and a collision shape as two of the important parts. Increasing them both should do the trick. Can you tell what exactly it is that you're trying to do ?
You should try increasing you Collision Shape along with the sprite using :
$CollisionShape2D.scale.x = Any value
$CollisionShape2D.scale.y = Any value