Reverse translations from these custom languages isn't easily possible because there is ambiguity in the reverse translation. It generally takes a human looking at it to figure out the meaning.Also note that Layonara has a few custom languages that will not appear on that page, and for those there are no online translators available.
For at least a couple of them, no, we don't want an online resource. They're languages even rarer than Abyssal/Infernal/Draconic/Celestial.Anyway, just offering that as a point of information.