I currently have a large amount of stranded inventory because one asin has merged with another.
Seller support are telling me to create a removal order and send to the new ASIN, surely there is a better way?
Facing the same issue 
Hmm. I am afraid that you will have to create a removal order and send under the new asin but maybe someone knows some unkown tricks to get it sorted 
merged listings can help streamline the buying process for customers and reduce clutter on the platform, they can also pose challenges for sellers.
Seller support should be able to relabel these (for a cost off course) and assign it to the new ASIN.
Try to open a new case to see if it’s possible.
They’ve done this for me before when my inventory went into stranded but this was after their investigation that I had sent the incorrect variation in. I gave them the correct ASIN and they sorted it for me.
As mentioned, they do offer re labeling.
In case I sent a product under wrong ASIN, can I contact them and they can relabel it in this case too or help me to fix it without removal order?