Create a new sprite Camera with ScrollTo behavior, remove this behavior from the player.
On every tick set Camera position to
X: clamp(Player.X, Rectangle.BBoxLeft+ViewportWidth("Platfomer")/2, Rectangle.BBoxRight-ViewportWidth("Platfomer")/2)
Y: clamp(Player.Y, Rectangle.BBoxTop+ViewportHeight("Platfomer")/2, Rectangle.BBoxBottom-ViewportHeight("Platfomer")/2)