What is the best way to migrate work definitions from a lower instance to Production?

Summary:

Suppose we have refreshed Test from Prod so now the two instances are identical.

In the Test instance, for each of 1000 items we create a new Work Definition (incrementing the Work Definition version in the process, from v1 to v2).

We now have 1000 items in Test each with a new Work Definition (v2) and we want to migrate these 1000 version 2 Work Definitions from Test to Prod (without typing them in by hand in Prod). What is the best way to do it?

Content (required):

Can we "Manage Work Definitions in a spreadsheet" downloading from Test, then copy the data to another spreadsheet and upload to Prod? (Our testing says "No, this won't work".)