I encountered this error message when trying to add a new column to the table earlier:
Saving changes is not allowed. Your changes require the following table to be deleted and recreated. You have made changes to the table that cannot be recreated or enabled the "Prevent saving changes that require the table to be recreated" option
Solution:
Tools -> Options -> Designer -> Table Designer and Database Designer Add
Prevent saving changes that require the table to be recreated Cancel the previous check
