This has come up a few times. I don’t know if there is a good solution for it.
https://forum.inaturalist.org/t/life-stages-missing-in-subclass-pterygota/53617/
https://forum.inaturalist.org/t/quickly-find-caterpillar-images/22397/
One possibility is to add such observations to this project: https://www.inaturalist.org/projects/larvae-of-endopterygota
Also, there are some observation field values that are linked to annotations. What this means is if you add an observation field with a relevant value (“caterpillar”, maybe “larva”), a corresponding annotation will be added to the observation once the observation has a community ID for which the annotation is valid.