Sure, there are a couple of ways; After saving my part in FZ, save you project, close FZ and reopen for the metadata to take effect. Click on the WeMos, then in the Inspector, under headers, click (male pins). It should just swap parts and maintain connections.
If that doesn't work;
After saving my part in FZ, go to \Fritzing\parts\svg\user\pcb and open WeMos-D1-Mini_pcb in a text/xml editor and copy the content. Open the other WeMos_pcb.svg part and past the content you just copied and save the .svg. You may need to save your project close FZ and reopen it to take effect.
EDIT: I just thought of another way to update the part if the first on doesn't work... Let me know how it turns out.
