If a chain has multiple locations using the same shared menu, then they can also have chain restaurant promotions that are created at the chain level and used by locations under the shared menu.
To add a promotion within a chain account, go to Marketing -> Promotions -> Group promotions and click on "Add promo deal":
The account holder will be prompted to select a menu from the available list:
Choose a promotion from the list and click on "Next":
For the next steps, configure the settings for the promotion and when this is done, enable it from the "Group promotions" section, like this: