Are you looking to document individual fields (e.g. .Temperature with Description "Degrees F"), or just at the actual UDT level?
I could see Extra Info and/or Description. Very helpful to document ALL .Temperature fields as "Degrees F" when you have a recipe block of 100 of them - just do it one place. Also, you could OVERRIDE the "default" UDT level Description/Extra Info in the Documentation Editor for an ACTUAL ELEMENT of a RecipeStruct Temperature field, e.g. assign "Actual Temp Deg F" for Recipe0.Temperature Description, where Recipe0 is the "current" recipe (Recipe1 thru Recipe99 are selectable recipes).