@steeljef With the identify search URL you can actually specify an existing list to use, without having to list individual taxon numbers in the URL. See
https://forum.inaturalist.org/t/how-to-use-inaturalists-search-urls-wiki/63#heading--multiple--taxa--list
For example, if I want to identify all non-research-grade observations of the taxa on my personal list of favorite taxa (everyone has their own such list as part of their profile), I just need to use
https://www.inaturalist.org/observations/identify?list_id=1028560
This is what a Collection Project would do if such projects were list-enabled, which they currently are not unfortunately.
You can create your own list from a CSV file at https://www.inaturalist.org/lists/new, then use the Add Batch option after the empty list is created. There may be some cross-walking to do between iNat taxonomy and some of the names you supply in the CSV before finalizing the list.