Permissions for Shopify App:

Here are the required permissions for the custom seller app:
Assigned fulfillment orders (Read and write)
write_assigned_fulfillment_orders , read_assigned_fulfillment_orders
Fulfillment services (Read and write)
# read_fulfillments, write_fulfillments
Inventory (Read and write)
# read_inventory, write_inventory
Locations (Read Access)
# read_locations
Order Editing (Read and write)
# read_orders, write_orders
Allow this permission if you want to sync the order details with the seller store once edited on the merchant’s store, else don’t allow it.
Orders (Read and write)
# read_orders, write_orders
Products (Read and write)
# read_products, write_product
View Written Guide