I don’t think it’s listed explicitly at either of the links, but the principle I’m using is that of hyphenating when you want to make clear that a compound is a compound, and not (e.g.) an adjective happening contingently to modify a noun.
Except Adj-Noun compounds are not actually productive in English. (Also, magnifying glass is arguably from “magnifying” the gerund, not the participle.)
Except Adj-Noun compounds are not actually productive in English. (Also, magnifying glass is arguably from “magnifying” the gerund, not the participle.)