Am asked to correct State ID exempt-div on Schedule B payer #3 & cant find a schedule B in my Turbotax return

During the error check, you can put in "XX"

Or you go back to the actual 1099-DIV entry section, and edit the forms...just step thru the various followup pages until it asks what state (or states) the Tax-exempt bond interest came "from".  the answer "More than one state" is always acceptable, and is at the end of the state's list.