System -> Every 2 seconds
Create Object platform on layer x at (player.X + 150, random(10, layoutHeight))
If you wanted the platforms to be random width and height, change it to the following:
System -> Every 2 seconds
Create Object platform on layer x at (player.X + 150, random(10, layoutHeight))
platform -> set width -> (random(20, 150))
platform -> set height -> (random(20, 150))