Yes thank you Mahesh.
This does work but this could be greatly simplified.
I would love to see a right click on the External Merge feature that I could browse to the new needed model file and import this.
The confusion with the present method is too great.
In your initial response Mahesh you didn't bring up the other method. This proves to me that this should be simplified as I'm sure many people also aren't aware of how this should be done correctly.