There are a fair amount of previous threads/posts on the forum about this that may be worth looking through. Some examples:
https://forum.inaturalist.org/t/how-do-i-add-individual-observations-to-a-static-list/12065/2
https://forum.inaturalist.org/t/add-search-feature-in-favorites/2502
But probably more out there with a more in-depth search.