To be absolutely sure, you could input a dummy flight and then see if there are lounges to which you have or think you have access. You can also do this for your actual flights.

If the lounge(s) you believe you have access to do not show on the list, then it should be fine to add it. But otherwise, better not to start adding lounges until you can be sure they do or do not exist. (Note: only the lounges to which you have access based on status/cabin will appear, so if you are not flying F the Concorde Room will not appear.)

In the event there are lounge duplicates, one of the administrators can make the necessary changes, but first checking should avoid that.

Also note that ba.97 and fbgdavidson have added just about every single lounge in the universe, so chances are the lounges already exists! ^