A-pose to T-Pose?

You can easily adjust the mannequin to be in the T-Pose as I’ve shown here (Be sure to select humanoin rig and to save pose once you’ve adjusted it.)

https://.unrealengine.com/showthread.php?83467-I-hate-the-A-Pose-mannequin

Important: When retargetting a Mixamo character, leave the Root bone blank. “Hips” should be the first bone you retarget.