Hi @wolfram06; this question has been brought up a few times previously in other threads. See eg https://forum.inaturalist.org/t/please-subdivide-lepidoptera-butterflies-moths-and-create-a-sub-order-lepidoptera-moths-only/12083 and https://forum.inaturalist.org/t/moths-not-a-search-option/8758
There are some good explanations in those threads as to why Heterocera is not a rank on iNat, largely revolving around the fact that it’s very much not a monophyletic group. There are some paraphyletic groups on iNat, but these tend to be very well-used groupings across many biodiversity data resources, whereas Heterocera is a taxon that is not recognised as valid across many databases.