Minecraft

Minecraft's snapshots and pre-releases (3.12.x and up)

If your modloader supports Minecraft snapshots or pre-releases, you can use those, too.

Simply set de.griefed.serverpackcreator.minecraft.snapshots in your serverpackcreator.properties to true

Then, when using the GUI, you will be able to select any weekly release, snapshot, pre-release and more, just like that.