It should still be possible to make the Custom Ore Slots apply to specific Dimensions, even though a little bit more complicated. The Config with the boolean for each Dimension will only show up once the World Generator actually generates an Ore in there, but you can then copy the Line for that Dimension into another Config to make it work that way if you know how.
And as I said the old Ore Generator with those 4 Ore Types per Vein is outdated and only exists in Dimensions other than the Overworld. I am not gonna do anything with the Old Stuff. It is just “there”.