KDE plasma crashes when trying to add empty space to the panel. This happened to me on FreeBSD 13 Current, and also the latest current FreeBSD 14.
The same issue was also reported in IRC some time ago, but I could not reproduce it on my machine.
There is also this upstream report for example
(In reply to Tobias C. Berner from comment #1)
It's like I try to make KDE have mac style layout, where you have a top Global menu + spacer + all other stuff clocks etc.
then it will crash once you add the spacer.
I had the FreeBSD-14.0-CURRENT-amd64-20210218-fa3bd463cee-256776 with the latest KDE avilable.
The bug report looks the same to me.
Thank you very much.
Also, I don't know whether this is a duplicate:
426269 – KDE crashed when adding/moving spacer in a panel
In upstream 422914 you can see a fix was merged for this, just in time for 5.21.4 which landed an hour ago. I closed upstream 426269 because that one was FreeBSD-reported, and am closing this one as "fixed" -- I posted upstream that I could reproduce it, and can no longer do so.