You can group sections together that you want to be included in the same order and prevent items from certain sections from being placed in an order with items from other sections e.g preventing retail items being added to orders with items from Dry Cleaning or Laundry sections.
To activate this setting go to Settings>Admin>Store Settings and scroll down to the setting "Activate Section Groups for New Orders" make sure this is activated and click the green Update button.
To group sections together go to Settings>Products>Sections and click on one of the blue "Choose Sections" buttons. You can then select all of the other sections that you want to be grouped with this section which will allow items from any of these sections to be added to a new order.
In this example Retail items will not be able to be added to orders that already include items from the Dry Cleaning section.
If you attempt to add an item from a section that is not grouped you will receive an error message.