the ItemTier has a new getter where you can return a Tag create a new Tag for this Tier, you can then use the TierSortingRegistry to add the Tier after the vanilla ones (not sure if "TierSortingRegistry" is the correct name)
With all due respect, that response is not helpful. I understand forge 1.12.2 is no longer officially supported. And I’m not asking for support from the official forge team.
What I am doing is inquiring about knowledge that someone may have and would be kind enough to share.