OS: openSUSE Tumbleweed 20180613 KDE Frameworks Version: 5.46.0 Qt Version: 5.11.0 Kernel Version: 4.16.12-3-default OS Type: 64-bit Reproducible: Always Steps to Reproduce: Make sure System Settings - Windows Management - KWin Scripts - MinimizeAll script and associated keyboard shortcut is disabled or even was not appointed. 1. Add "Minimize all Windows" applet to the Desktop or to the Plasma Panel. 2. Open "Minimize all Windows" context menu and click "Configure Minimize all Windows". 3. Add keyboard shortcut (for example Meta+Shift+D). 4. Use "Minimize all Windows" applet by a keyboard shortcut or by clicking on it's icon located on the Desktop or the Default Plasma Panel. Actual Results: The "Minimize all Windows" applet only minimizes windows but does not restore them by the second click or keyboard shortcut. Expected Results: The "Minimize all Windows" applet should restore windows by the second click or by keyboard shortcut.
Probably the enabling of the option "Keep window thumbnails - Always" (System Settings - Display and Monitor - Compositor - Keep window thumbnails - Always) is the trigger of this error (or misbehavior).
*** This bug has been marked as a duplicate of bug 413044 ***