You can now override on a per-customer group basis if invoices and credit notes that you've issued to a customer in that group should be synced to your accountancy provider as the customer group or as the individual customer. To toggle this option, simply go to the customer group and change the "Where would you like invoices and credit notes issued to this group's customers to be synced?" setting.

This allows you to override the default "Upload customer groups instead of sub-customers" option in your accountancy integration settings for a customer group.