SUMMARY
According https://docs.kde.org/stable5/en/kalarm/kalarm/create-edit.html#calendars (search for the heading "Storage type") is claimed:
> KAlarm handles two alarm calendar storage types:
> …
> Local directory: Alarms are stored in a local folder, each alarm being stored in a separate iCalendar file within the folder. 
> This storage method has the advantage that in the event of file corruption, you should lose only one alarm, 
> not the entire calendar.

Exactly for that reason I wanted to create a "Local directory" calendar but »kalarm« only allows to choose a 
local ICS file (i.e. all events lumped together within a single).


STEPS TO REPRODUCE
1. open »kalarm« and add a new calendar
2. the popup window only allows to select a single ICS file, not a directory and provides no way to create a "Local directory" calendar.

OBSERVED RESULT
No option to add a "Local directory" calendar in contrast to documentation:

> Add...
>
>    Add a calendar of the selected type to the list. You are asked to choose a storage type, following which the calendar 
> configuration dialog is displayed, where you can enter the location of the calendar and its characteristics. If there is no 
> existing alarm calendar in the specified location, a new one will be created.

EXPECTED RESULT
»kalarm« provides the choice of storage type as documented and implements adding "Local directory" calendars.
(much less prefered solution: documentation is corrected … ;-)

SOFTWARE/OS VERSIONS
[copied from System Information]
Operating System: openSUSE Leap 15.5
KDE Plasma Version: 5.27.9
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 5.14.21-150500.55.44-default (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i5-10210U CPU @ 1.60GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics