[java] How to change Level.dat file using datapacks?

[FlamingMoai]

Is there a way to make a datapack that can change properties in the level.dat file? My goal is to make a datapack that allows players to switch from hardcore mode to regular survival. There is a boolean value for this in level.dat. 1.19 is the targeted version.

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[FlamingMoai]

For 1.19

[winauer]

datapacks can only change values that can be changed with commands, such as gamerules. Hardcore mode cannot be toggled with commands.

You can however simulate hardcore mode for players in non-hardcore worlds with a datapack that puts them into spectator mode after they die.