I've been setting up a Dell XPS15-9550 today. It comes with Windows 10 and the most awful Dell addin you have ever seen. I normally use Dell because they refrain from adding too much crapware or useless third party apps. However, this addin, enabled by default, is awful. It adds a popup menu whenever you try and drag a window (or dialog box or popup borderless window) to reposition it on the screen. It's totally unnecessary as Windows 10 already includes a perfectly good "Windows Snap" feature. The popup window is always "in the way" and when you release the mouse the window then flies off to an illogical place on the screen. Truly awful UI design.
Finally I've worked out how to stop it. It turns out it's a feature of "Dell PremierColor". To disable this right click on the "Dell PremierColor" icon in the notification area and select "Disable Display Splitter".
Why oh why are you including this enabled by default? Crazy. Please ensure it is disabled by default ASAP at it is confusing and totally unnecessary.