I’m not totally sure how easy the NodeRed implementation makes it, but the basic idea is to include a PropertySet on each metric in the NBIRTH/DBIRTH message, and use the “JSON/Scripting Name” from the Ignition tag properties documentation as the keys.
Some are filtered out by MQTT Engine by default, but things like engUnit/engLow/engHigh/documentation are definitely allowed through. The values to set each property to also mostly follow that document, but there are a few exceptions.