How to migrate EM UDMs to 12c?

So I've migrated my Grid Control 10g to Cloud Control 12c. Several minor issues, a few major ones, but it's working.

One piece I overlooked (probably because the documentation only mentions it in passing on page 27-1 of the Upgrade Guide) is that my user-defined metrics were not ported over. OK, I'll grab the SQL from the XML on the old 10g Agent and recreate it in 12c. But of course there doesn't appear to be a way to exactly recreate this as a UDM in 12c as they have been superseded by Metric Extensions.

The UDM page in EM 12c says: "Existing User-Defined Metrics may still work, but should be converted to Metric Extensions to ensure future compatibility.", but I'm not able to find where to create the UDM, if possible.

My concern is the effective loss of 3 years of metric information. Has anyone done this? What did you do? I'm more than a little bummed that I'm only discovering this after completing the migration...

TIA,
Rich

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