The hidden visibility setting in the system tray settings window aren't saved unless the application represented by the entry is closed once during the session in which the changes have been made. Reproducible: Always Steps to Reproduce: 1. Toggle visibility to "Hidden" of entries in system tray settings 2. Logout 3. Login
does this happen only for entries that are applications or also entries that are plasmoids? (such as audio,battery, clipboard)
After some more investigation, it seems that the hiddenItems field in the configuration file ~/.config/plasma-org.kde.plasma.desktop-appletsrc seems to be populated with more and more entries: "hiddenItems=10485813,50335619,35651636,41944964,35651637,48236384,58720275,qBittorrent,71303177,41943911,46137352,37748789,54525956,35651682,44040200,39845940,33554485,48234515,46137348,48234500,69217378,37748834,60820430,62916533,62919417,62949545,58720260,46137407,QuiteRss,83886307,50331667,60817417,60817412,48234559,52429027,52428804,39846001,44040419,41943048,117441896,144703551,44040255,94371903,83886089,39846115,35651697,12583897,41943267,48234504,62914569,50331652" I suspect this to be the root of the problem. Somehow the mechanism to detect the same application across sessions fails to work properly: known applications, for which visibility has been specifically configured, are not recognized and a new identifier is created. It only happens for entries that are applications.
To elaborate on this: "The hidden visibility setting in the system tray settings window aren't saved unless the application represented by the entry is closed once during the session in which the changes have been made."; I know believe this to be inaccurate and something else (the identifier generation) is responsible for it working or not. Sometimes it does, often a new identifier is created and it doesn't.
*** Bug 378910 has been marked as a duplicate of this bug. ***
I think the original issue described here has been fixed. I can only reproduce this issue with Dropbox, not any other apps in the tray. After investigating why Dropbox seems to be affected by it, it seems like a Dropbox problem: $ grep hiddenItems ~/.config/plasma-org.kde.plasma.desktop-appletsrc hiddenItems=org.kde.plasma.mediacontroller,dropbox-client-1764,org.kde.plasma.clipboard,org.kde.plasma.vault,dropbox-client-1447,dropbox-client-3761 Looks like Dropbox's executable name changes with each login, so the strings don't match. If you actually do succeed in getting Dropbox permanently hidden by hiding it and then quitting and restarting it, it disappears entirely, which is Bug 361613.