check out my post, i used PKNX to edit my encounter tables for sword and added the shield exclusives to where they are appropriate and added the 30ish pokemon that are coming with Pokemon Home to them too.
gbatemp.net/threads/pokemon-sword-modified-encounter-tables.553933/
EDITS: didnt see that you wanted shield encounter tables, but im sure you just need to change the titles id to shield and it should works fine.