This feature would allow community creators to remove all the players who quit 6 months ago. Right now big communities end up dying because there’s a 1000 player limit and unable to see who isn’t playing anymore.
You can suggest ideas ingame via the support menu (submit feedback or wow report). Support do not implement new features into the game nor do they forward feedback to devs.
like Chronormi suggested this suggestion is best admitted in game, however, a current work around would be if everyone updated their note monthly with d/m/y when they were last online. this way its easier to track who is active and who isnt.