Thanks to our internal hackathon, the ability to convert stories to defects is now available! Similar to story -> PI conversion and defect -> story conversion, this option is also available in the action menu. Because of some differences between stories and defects, the story will remain open and continue to keep it's children after the conversion is complete.
To use this new conversion, check the action menu on stories to find the the "Convert to Defect" option. Give it a try and let us know what you think!