Using a laptop with kubuntu trusty. I have a single panel on the monitor of my laptop. I occasionally connect a second monitor, which I have previously set up a panel on. If I connect this monitor while plasma is already running, I can not access "panel settings" on the panel on that second monitor. When I select the item, i see the panel settings pop for a split second, then disappear again. If I kill plasma-desktop and relaunch it, the issue is gone. Unless I remove the monitor an plug it in again. Reproducible: Always Steps to Reproduce: 1. Connect a second monitor 2. Set up a panel on the second monitor 3. Disconnect the monitor 4. Wait a few seconds 5. Connect the second monitor again 6. Attempt to use "panel settings"
Plasma 4 has been unsupported for several years. If this reproduces in Plasma 5, please re-open and set the product to "plasmashell | panel"