In KDE 4, the kOrganizer main window would appear when clicking (or double-clicking?) the reminder systray icon - sometimes it would appear behind existing windows, but it would open. This does not seem to happen any more with kOrganizer 5, forcing me to start the application via krunner instead of just clicking the tray icon. Inconvenient. Reproducible: Always
Still valid ?
Yes, at least with the kOrganizer version I've installed - which is, as far as I know, the most recent precompiled version you can get for (K)Ubuntu: ii korganizer 4:15.08.3-0ubuntu1~ubuntu15.10~ppa1 amd64 calendar and personal organizer No idea if there are more recent versions in source form which already fix this.
This is still valid as of: ii korganizer 4:15.12.3-0ubuntu1 amd64 calendar and personal organizer
Seems to be fixed as of kOrganizer Version 5.3.0 (QtWebEngine) (KDE Neon packages).