System tray should have an option to always show/hide ALL icons. Configuring it every time you have a new program that makes icon there is not an interesting way to spend time.
Probably WONTFIX for Plasma 4, see reviews at https://git.reviewboard.kde.org/r/100743/ Requested for Plasma 5 as bug #349812
Hello! This feature request was filed for KDE Plasma 4, which reached end-of-support status in August 2015. KDE Plasma 5's desktop shell has been almost completely rewritten for better performance and usability, so it is likely that this feature request is already implemented in Plasma 5, or is no longer applicable. Accordingly, we hope you understand why we must close this feature request. If the requested feature is still desired but not implemented in KDE Plasma 5.12 or later, please feel free to open a new ticket in the "plasmashell" product after reading https://community.kde.org/Get_Involved/Bug_Reporting If you would like to get involved in KDE's bug triaging effort so that future mass bug closes like this are less likely, please read https://community.kde.org/Get_Involved#Bug_Triaging Thanks for your understanding! Nate Graham