@AngeIV this test was only intented to present a possible way to simply just copy the pelvis motions on the x and y axes to the root bone, and to align the IK bones which can help in certain procedural behavior (eg foot, hand IK). I was hoping that the retargeting can be extended as such to allow these copied bone transforms to be actually baked on the animation sequence thus allowing the mixamo animations to use the root and ik bones a fairly good way.
I’m not sure if that is actually possible to do in ue4, but you can perhaps bring the exported mixamo animations straight into maya and bake them on the ue4 mannequin with a good receipe (scripting?) thus allowing these bones to inherit the motions you are willing to see. Upon importing the baked animation sequences into ue4 you should be able to use the retargeted mixamo character, or any skeleton that have the root and ik bones available.