This would allow the user to customize the system tray icons order and to hide these icons by dragging them to the arrow icon (just like in Windows, when you drag an system tray icon nearer to the arrow icon, a popup opens and you can drop the icon inside it to hide it).
Seems to be a good idea or rather an intuitive way to do this (ease of use).
This would be wonderful! It's definitely a long-requested feature by the community, as evidenced by simply googling "kde system tray order" (there are posts from over 10 years ago!). I've wanted this for a very long time myself, it's probably my biggest pet peeve with plasma. It feels like a very natural feature to have.
*** This bug has been marked as a duplicate of bug 384782 ***