After rooting through the source for the Unit definitions, I found this. Looks like the the categories.ts defines the Categories and for Unit names, and then imports the formatting functions from the files listed at the top (in the same folder).
My question is this: Can I leverage a plugin to expand on this list, creating new categories, new units, and defining new functions to format the data? If so, would that be a panel plugin? I’m not asking for a bunch of hand-holding, I’m just hoping for a direction, though any clues would be eagerly accepted.