Return value from a different table

Jawed If you have only 1 "indexed Type" by "Subaccount name" I believe it would make more sense to keep have an "Indexed Type" column in your "Subaccount name" table.
Usually those "link" table are created in power query by removing duplicates in another table and if this is the case, you can just keep the "Indexed Type" column.

However if for some reason that doesn't fit what you want to do, you can access the value with the below DAX formula after selection "Add New Column" in your "Actuals" table:

Indexed Type= 
var Suba=RELATED('Subaccount Name'[Subaccount Name])
var indexed=FIRSTNONBLANK(SELECTCOLUMNS(FILTER('CoA,'CoA'[Subaccount Name]=indexed),"Index",'Subaccount Name'[Subaccount Name]),"Index")
return indexed