My Korganizer is not usable. I am unable to do add calendars or events.
When I launched it the first time, it showed two calendars - Birthdays and Personal Calendar.
I tried setting up another local calendar. But it would not let me.
When I was trying different options, I accidentally deleted both Birthdays and Personal Calendar.
I tried getting them back, but could get only the Birthdays. There is just no option for Personal Calendar.
And now, when I try to add an event, it gives an error like this:
How do I get this working?
There is no data is Korganizer currently. So, I do not mind a complete reset as an option. How do I do that?
Your screen shot of adding an event shows no choice for a calendar in the dropdown box. That is the cause of the "Select a valid collection first." message. Your main Calendar window shows Birthdays and Anniversaries which should show up in the Event Creation box Calendar dropdown box. It doesn't - which indicates a corruption in your configuration. As you do not have any events yet, I recommend uninstalling and reinstalling Korganizer using your Software Center client (e.g., Discover in Kubuntu). In setting up your calendars anew, it might be helpful to work your way through the Korganizer Handbook:
https://docs.kde.org/trunk5/en/pim/korganizer/index.html
I had some time to figure out how to add more calendars . The only one way i found is :