What you want would require a database of all spells you want to see on that window, and then the window would need to compare the maintained spell name against this database and hide the icon if there is no match. It would also have to check the target of the maintained spell and compare it to the members of your group and your raid, and if there is a match, hide the icon.
So in theory it's doable. Maybe someone will create that for you (I won't).
PS: I have no clue why you would want to spam chat with the duration of your maintained spells but that could be done as well, and unless I'm missing something that would be allowed in view of the EULA.