It’s not shown in the list of search options, but it’s still available. If you’re on a PC, you can run the search you want in Identify and then copy the search parameters part of the URL into Explore. For example, I copied the nymph parameters back into Explore and got this: https://www.inaturalist.org/observations?term_id=1&term_value_id=5.
See more at the Search help wiki.