openSUSE Leap 42.2 -- plasma5-workspace: 5.8.6-8.1 (LTS) Linux (x86_64) release 4.4.57-18.3-default KOrganizer: Version 5.3.0 (QtWebEngine) Under: - KDE Frameworks 5.26.0 - Qt 5.6.1 (compiled against 5.6.1) - The xcb window system If in the Calendar management window, an ICS (file) calendar is selected by means of "right click", the "default calendar" selection doesn't work. Subsequent creation of events or To-dos are initially proposed for entry in another calendar rather than the calendar file which one wishes to use as the default calendar. Please note that, I do not have a "std.ics" file -- I tend to use multiple files, one per year for archiving reasons. - Typical calendar file names are: xxx_2012.ics; xxx_2013.ics; xxx_2014.ics.
With the following KDE components (openSUSE Leap 15.0) this issue seems to have been resolved: KDE: 5.45.0 plasmashell 5.12.5 Qt: 5.9.4 Now closing this issue.