Sorry, you didn't understand what I mean.
You go to Administrative to designate thread that will be used as garbage thread. This is usually done once or rarely. And by moderator if it can be done from front end.
If it's done from back end, moderator needs to tell me (or any other admin with privileges to do so) which thread he wants to use in his forum and I need to go in ACP, forum manager, find forum and enter thread info there.
So I thought, if it could be done to leave that to moderators, that they themselves decide which thread they want to use and that they do actual designation of thread as garbage thread, i.e. one job less for us administrators.
Of course, actual moving of posts is done by clicking on image in posts. And they go to thread moderator designated, hopefully from front end.