Use World Seed

I found this, for 1.18.2:

 world.getServer().getWorldData().worldGenSettings().seed()

It returns current world's seed in a variable of type Long.

Use a Custom code snippet.

If you want to convert it to a variable of type Int or Double, DON'T do this:

(int)(world.getServer().getWorldData().worldGenSettings().seed())
(double)(world.getServer().getWorldData().worldGenSettings().seed())

It will return a different value to your seed.
Instead, first convert the Long variable to a String, and then parse it.

Int.ParseInt(world.getServer().getWorldData().worldGenSettings().seed() + "")
Double.ParseDouble(world.getServer().getWorldData().worldGenSettings().seed() + "")

I hope this is helpful to you.

Sorry, it's not Int.ParseInt() or Double.ParseDouble(). It's Integer.parseInt() and Double.parseDouble()

ShadowGriff872 does this work for Mcreator 2023.2? If so, how do I make it work?