I’m pretty new to Metahuman and I’ve tried following a tut on exporting Blender hair to UE5.3. However it didnt work when I tried. So I’m hopeing maybe in the very near future MH may update their catalogue on hairstyles or at least make it easier to style the hair either in UE5 or in Metahuman designer its self.
I can relate. I am having a difficult time with the hair too and my character losing his eye brows every time I try to create something. 
You can get the eyebrows back by creating a new binding to your new head. Reset eyebrows and binding so its empty. Then find the original eyebrows, right click create new binding on the eyebrows, click your new head in the dropdown box that appears. A new binding will appear in your content. Drag the eyebrows into your characters blueprint under where eyebrows should be and drag the binding in the box underneath where it says binding.
Your eyebrows should be back now. 