Ok I see. There is no way to do what you want using custom info/headers as you would in custom entries. However, I think you could do this if you wanted all of your custom information to appear next to each other, as you could enter a new line into the Note and then use text codes to mimic the labels of other pieces of information. For example you could put this for the notetag (if your label color was 1):
<cgmzdesc:This enemy is frequently encountered in the Plains.
\c[1]Level:\c[0] 20>
And then it would appear as if you had a custom level parameter being displayed, even though really it's just continued from the note.