You could add a switch expression to perhaps have a top 10 list and then the remaining will be sorted alphabetically
Sort(["UK","New Zealand","Australia"],Switch(Value,"UK","0","Australia","1",Value))
Or
SortByColumns(AddColumns(["Italy","UK", "Australia","Denmark"] As Countries, "CustomSortOrder",LookUp([{SortOrder:"1",Country:"UK"}], Country=Countries.Value).SortOrder),"CustomSortOrder",SortOrder.Ascending,"Value")
