I dunno. The tag capability is there, you just have to duplicate it for this purpose. It would effectively replace the favourites system, because you could add your own tags to obs, which would be visible on the observation page only to yourself, and you could click those to go to a search result that matches, just like you do for the tags now. Once you “check this one later”, you can delete the tag to have it drop off that category, so to speak… I would imagine that instead of adding tags at the time of uploading the observation, the IDer tags could be added at the time you make the identification (on the identify page) or directly from the observation view, in a similar way that the observer can add them to their own observations.
Just thinking outside the box, because the two tag systems would be near identical in how they operate, maybe there could be the ability to “publish” tags and make them searchable under both systems. They would by default be private to the tag setter, but they could toggle them to be openly searchable. There are many users that include tags for a number of useful things that could benefit others, like flower colour, or being from a particular reserve, etc. It then becomes borderline like the field system, with the ability to have them remain locked and controllable by the setter (eg an identifier).