Custom Superflat Preset Codes Wont Work!

When i try to put in a custom superflat code it doesn't show my custom code on the list.

I am trying to do-

3;20*minecraft:stained_glass:0,10*minecraft:wool:0,7*minecraft:quartz_block,5*minecraft:iron_block;1;village,mineshaft(chance=0.01),stronghold(chance=32 count=3 spread=3),biome_1(distance=32),dungeon,decoration,lake,lava_lake

Why wont this work and can you help me!!!