The Gelatin Crystal will generate in worlds created prior to 18.104.22.168 as well as after, so it is not necessary to create a new world to obtain it.
Similar to Crystal Shards, Gelatin Crystals can be quickly farmed by placing rows of Pearlstone Blocks or Pink Ice Blocks in straight lines in the Underground Hallow.
Unlike Plantera's Bulbs, another type of naturally spawning boss-summoning item, Gelatin Crystals' generation do not have a minimum distance restriction between each other. This can lead to two or more of them generating very close together.
Despite the difference, the Gelatin Crystal will be identified as a Crystal Shard by the minimap.