How can I combine different morph targets?

I got a character model with morph targets both in her mouth/teeth/tongue and I’m using a plugin called ovrlipsync to lipsync her when I play an audio or speak to mic.
How can I combine both morph targets of teeth and tongue at the same time when the mouth is moving? It seems like you cannot edit morph targets in the skeletal mesh window in ue4.
I’ve tried two method to realize this:
1.I connect the blend shape of teeth and tongue to mouth in Maya’s original file and export the fbx, then import to ue4. But it seems like the connection is lost and all those morph targets can only be adjusted separately.(even the names of those morph targets have been changed into some Shape1 Shape2…ect, don’t know why)
2. I draw the BP in the lipsync part like this… I know the right part looks kind of stupid and totally in a mess but actually it worked…but not in the correct way. Teeth and tongues’ are not in the right position. So anyone can help me to figure it out?