I feel like I’m taking crazy pills here. I right click on panel, “Add or Manage widgets”, desktop goes into edit mode (reduced size screen shown, can enter the panel configuration, etc)… again click on top left “Add or Manage Widgets”, just does nothing. I feel like I could be doing something wrong, but I’ve run KDE for years and I can’t get the Add Widgets window to show up.
EDIT: Solved, I hadn’t rebooted since updating KDE packages. Once restarted, “Add or Manage widgets” screen shows up fine. I’ll leave this here for people of my or lower IQ.