Go to your cartographer, select random world.
This gives you the prompt to enter a world seed with the following warning: Creating a new world will erase any existing save file.
Edit: After doing this you may need to start new game, and select “existing world” instead of a random one.
@EradicateYou I did see that warning when I started my latest game about it erasing any existing save file… I was kind of worried that it would Wipe out my previous saves… Am I correct that it only erases the current save slot, and not all save slots?
Randomising the world (changing the seed number) will overwrite the existing save slot. So if say you decide to randomise slot 2, any previous save data on that slot will be erased.
I can understand “Any existing save” can be read as all save slots or just the save in that particular slot. But before you select the random world option, if you just highlight it, there is a small info warning under the map that says “Randomise the world for the current slot”. Just make sure if you were playing on multiple slots, you are randomising the right one!
If you want to take extra precautions (change of mind etc), if you are playing on a PS4 you can back saves up to a USB or external drive first.