This isn't really an idea for a specific SCP and more of a suggestion for a concept, I guess, so I apologize if this is the wrong place for it. But lately after thinking about the other lists and designations that the Foundation has, like the logs for anomalous objects, events, or ducks, and the -Ex designation for explained SCPs, I feel like the site is missing a big one, for objects either not yet contained or that have escaped containment. It could either be done as list with short entries for each object, like the logs mentioned before, or maybe as a new designation, like -Ex, with Proposed Containment Procedures and more "appears to be" rather than "is" in the description, as well as details about its current or suspected location, what efforts are being undertaken to contain it, and why the Foundation hasn't been able to contain it yet.
In-universe, it just makes sense for the Foundation to keep documents on these. In terms of story and creepypasta, one of the things I've turned to when feeling creeped out by the thought of 173 or 108 getting me is that the Foundation has these baddies contained. So what happens when you read about something that's out there, that could be in your room right now? It shows that the Foundation is just as fallible as anything else for whatever reasons.
Obviously if it was used as a special designation, it would have to be exceptionally good, just like with the -Ex and -J SCPs. I have to admit I don't personally have any more specific ideas for this, and this is more me just throwing the idea out there for anyone who'd want to use it. Again, sorry if this isn't the right place for that.