This video goes different tips and tricks with IK Retargeting that users may use outside of retargeting bipedal characters. While not all of these tips and tricks are available for UEFN users/are necessary, it is important to show due to the different usecases of retargeting. This video will be updated with any new features and updates that may help for any retargeting needs.
https://dev.epicgames.com/community/learning/tutorials/oMXP/unreal-engine-fortnite-ik-retargeting-additional-tips-and-tricks