At the shipping selection tab, you can configure which shipping methods are available for a specific vendor and check the vendor’s currently selected shipping methods.
This allows you to configure several shipping methods vendors can use without the hassle of creating or configuring a shipping method themselves.
You need to select “Global Shipping Methods (Vendor Selectable)” at the “Shipping Method Selection” tab, to use the shipping selection settings.
The select vendor section:

Use the select vendor section, to check the selected shipping methods of a vendor. When you choose a vendor from the dropdown list, the shipping method selection list will be populated with all the shops global shipping methods.
Shipping methods, the selected vendor has chosen, will appear as selected.
The shipping methods selection list:

Please note: At least one shipping method should be selected. If none are selected, all shipping methods listed will be available for the selected vendor during checkout.