When editing an account, you will find the following advanced settings...
When enabled, these settings provide extra functionality in certain sections of your store toolbox. These are detailed below.
Enabling advanced theme options allows you to set custom image sizes for your products. This section is displayed in the "Design & Assets -> Theme Editor section of your toolbox.
Enabling advanced shipping options allows you to create "Shipping Codes" for your products, so a single product or a group of products can be set to have their own shipping cost. Further information about Shipping codes can be found at Shipping Code based Shipping Rates
Enabling advanced checkout options allows you to enable customer account numbers in your store. A Customer Account Number may be optionally added to the checkout pages if you want to request that a customer provides an account number when checking out.
When this option is enabled, an additional entry field will appear on the first checkout page and this will allow a customer to enter their account number. You may select whether this field is required or optional.
Refer to the Knowledge Base article Checkout & Payment for further information.
Enabling advanced product options allows a few different options. These include;