Can I give my head chef manager rights on the POS without giving him a dashboard login?

Yes. The two lists are separate. On Settings → The POS, under People at the POS, add him with What they may do set to Sell, and approve discounts. He can then approve a refund, cancel a printed sale or close a shift over unpaid tables by tapping his name and typing his four numbers, without ever seeing the dashboard. A dashboard login is an email and a password made under Settings → Team, and it opens the menu, the orders and the reports in a browser. Neither one grants the other. Restaurant staffing software here keeps the counter and the office apart on purpose.