Whole body preview mesh method;
-Create your animation in sequencer.
(Make sure you save)
-In your metahuman blueprint click on the body component on the left hand side.
-On the details pane on the right hand side under mesh select your preview mesh that matches your current mesh, it will be named the same but with preview at the end.
-Then back in sequencer right click the body track and bake animation sequence.
-Chose where to save your animation sequence.
-In the content browser find your animation sequence and right click, go to asset actions and export.
-Make sure you select include preview mesh in the output options box.
-You should now be able to import in to Marvelous designer.
Hope this helps