This is a special case CVar that allows us to use CVar conditions to maintain behavior with legacy device profilesDo not use directly for new contentLegacy device profiles can be given a specific value for this CVarand then CVar conditions used to enable / disable as appropriate to match with legacy assets with enabled / disabled content based on them.
Usage
fx.Niagara.LegacyDeviceProfile [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.
