SUMMARY Floating panels cannot be pinned anymore after making them floating STEPS TO REPRODUCE 1. Open a panel via Settings -> Show Panels 2. Drag a panel or click on the diamond icon in the panel 3. The panel is now floating, and there is no (obvious) way to to make them pinned SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Plasma Version: 5.27.4 KDE Frameworks Version: 5.105.0 Qt Version: 5.15.9
Floating panels can be re-attached to the main window by grabbing them at their own small title bars with your mouse cursor and dragging them towards the left or right border of the main window. Then, in the main window some visual feedback is shown where the panel will be placed if you release the mouse button. I'll attach some screenshots for demonstration.
Created attachment 158338 [details] KBibTeX main window with detached panel
Created attachment 158339 [details] KBibTeX main window showing location where panel will be placed if mouse button gets released
Created attachment 158340 [details] KBibTeX main window with re-attached dock