On the Biome slider (the one that says "Biome: All" by default) in the basic Settings of the customized menu not all of the biomes are listed in the slider, some are missing (ex: Ice Plains Spikes, Sunflower Plains, etc...). I wanted to create a world with only Ice plains Spikes biome in it (and rivers).
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However, this issue is a Duplicate of MC-55813.
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