Switch doesn't yet have 1.6 and the terraria easter egg involving the doll on level 100 is a 1.6 feature, unfortunately you'll just have to wait until the update drops on consoles.
When it does though, a tip is that it is thrown into the lava like one would throw a fish into a fish pond, NOT out of the inventory into the lava (I lost 4-5 dolls trying to figure out why it wasn't working)