Woocommerce has launched their official shipment tracking plugin.

Please make click and drop compatible with it rather than sending tracking details via an outdated method:

API documentation:

https://woocommerce.com/document/shipment-tracking/

Alternatively, allow the sending of tracking details via order notes without marking the order as complete on woocommerce

OR

First send the tracking details into the order notes and THEN mark the order as complete.

All of the above allows tracking details to be embedded into the complete order email. RM's current solution does not.