Undocking tabbed widget from floating window creates empty redundant window
Screencasts showing broken behavior with https://codereview.qt-project.org/c/qt/qtbase/+/516878
Undocking a QDockWidgetGroupWindow from QMainWindow, followed by undocking one tab from the group window (keeping tab in a dragging state), followed by re-docking that tab to any location will result in the tab you are docking to instead be docked to the QMainWindow in the same position that the group window was docked. See screencast 516878-27-redock-to-floating-dockwidget-docks-qmainwindow.webm