I am not a curator, but I do not think one needs to be a curator to edit the list. On the right side of the page at:
https://www.inaturalist.org/check_lists/2016024-Interreg-IT-FR-Marittimo-Check-List
is a green “Add to List” button and it appears anyone can add any species. Someone correct me if I am in error!
I gather that lists in general have been problematic and this functionality is apparently not slated to see much in the way of support. Although the post relates to personal lists, I am guessing that under the hood may be some sort of common “list” object that is being used. Having read a number of a topics including the differences between ebird and iNaturalist I have come away with the impression that lists are intentionally not a focus of iNaturalist. Lists are not seen as being socially interactive, and the iNaturalist team seems to have a focus on elements that engage the community on iNaturalist in conversations about nature. Just my opinion!