Problem solved!
For anyone interested I found this answer in the TTax forums.
I discovered I needed to simply delete the original asset then add its constituent parts as outlined here:
https://ttlc.intuit.com/community/business-taxes/discussion/manu[product key removed]ciation/00/1317...
My thanks to EXPERT AnnetteB6 for this simple solution.
I was seeing the issue incorrectly. I was attempting (incorrectly) to modify an existing old asset.
As always, things become much simpler once you see the explanation.
