I've marked this as solved. Whilst I didn't get a perfect / ideal answer, I Did some good responses and enough information to make a decision for my use case. In the end I decided that a refactor would be too much work, and while i came up with other more elegant solutions, they really all just boiled down to an extra call to setGeometry, so i ended up going with the existing fix. Thanks everyone though.

@Christian-Ehrlicher Thank you, it helped! In fact, these two commits contained what I needed: Fix dragging a docked QDockWidget [REG-fix] 430985: Refix QDockwidget drag out dockwidget

@SGaist Thank you very much for the quick reply. I've removed both the horizontal and vertical layout boxes and everything works exactly as I want. Sometimes newbies make life more complicated for themselves than it needs to be! Thanks again!

@eduardo_parra said: but the cursor detect the margins What margins? Do you mean for something inside the docks?

@MrKozmon I'm having the exact same problem on Android. When I drag a QQuickWidget that is hosting a QML-based WebView on Android, the widget moves but the WebView is left in the original position. Wondering if there has been any progress or a workaround for this issue. I am using Qt 5.10.0, developing for an x86 Android platform.