You can search the level below and the level above the desired key level and the keys containing the desired level as a substring will come up. For example, searching “12 14” will yield only level 13 keys. This is because searching a number includes one level above and below, and the number in between the higher and lower entries is the only one meeting both conditions.
Additionally, here is a lovely addon that may provide what you’re looking for: https://www.curseforge.com/wow/addons/premade-groups-filter
You can filter by key level type in that number. You than get that key and +1 or -1. Otherwise do as the person above said.
The system auto filters groups that don’t have room for you or your group based on your current roles by placing them at the bottem when you refresh. Eg as a tank groups that have a tank are auto placed at the bottem. If I group with a healer any group with a tank or healer or both is placed at the bottem below groups that have only dps.
If you want to see only +14 keys then search “13 15” and it will only give 14 keys. Because wen you search a number it will give you plus and minus 1 of that number and 14 is the overlap of 13 and 15.
That’s good info, thanks for posting! I knew about the filtering of key levels but I did not know about how it filters groups that may not have room. Sure wish this was explained a bit better in game though.