one advantage of the bookmark method, is you can have subfolders within folders. I have an iNat folder that I throw all iNat related bookmarks into, and then it is broken down into “literature”, “tools”, “cool observations”, “Projects”, “rainy day”, and so on… “rainy day” is my “come back to” folder! The “Projects” folder is where I put stuff directly related to specific projects I am working on and I usually move that bookmark folder to the main bookmarks bar so that it is “always accessible” while I am working on a project, and then drop the folder into the “iNat - Projects” folder once I am mostly done with it. I also have all my “saved Identify filters” bookmarked into a seperate folder, so I can easily switch between working on different ID workflows.
I say this, because you could create subfolders for the different reasons for which you would want to come back to an observation. If a particular subset of them require a certain book to be borrowed from the local library, then make it a subfolder that you can go back to when you have that book, or it might be “show these ones to Joe”, a friend that is not on iNat that visits you from time to time that might be particularly good on certain types of observations, etc. You can rename the bookmarks to things like “check if pustule is large enough for Sidymella angulata” etc