There is no standardized way to do this, but many users use observation fields (e.g. “similar observation set”) or tags for such cases.
Some relevant threads:
Feaure request: https://forum.inaturalist.org/t/link-observations/1367
Tutorial: https://forum.inaturalist.org/t/using-the-field-similar-observation-set-for-linking-observations-of-lepidoptera-when-raising-on/1018
Other discussions:
https://forum.inaturalist.org/t/uploading-observations-of-the-same-individual-over-time/2956
https://forum.inaturalist.org/t/how-to-indicate-one-individual-across-multiple-life-stages/46089
https://forum.inaturalist.org/t/repeat-observations-same-individual-how-to-submit/4252/2
https://forum.inaturalist.org/t/follow-up-observations-for-an-individual/3282/2