The notification area properties allows for the hiding of entries, but by default they are always shown and it would be good to have an option that would always hide new entries which are unhideable by clicking the expansion arrow.
What would be the use case for such an option?
I presently have 8 icons in my system tray area and would prefer that no new ones appear in the location unless I explicitly enable it. I will still have access to them as the hidden arrow is present and I can toggle it to show them.
Sorry, that sounds like a personal preference, not like a general use case.