I am using KDE Plasma on Debian Sid. I tried to edit the desktop background to add some widgets. However, it doesn't seem to work as no widgets are showing up in the list. I restarted the machine and yet the problem persists. I am attaching a screenshot. Any idea as to how I can deal with this?

It's not that the widgets are not there. If I click somewhere in the widgets list, then they appear on the desktop. It's just that they don't show up.