You need to define a program shortcut key. It's not set by default.
Open the full Dell Display Manager user interface. Look for the settings related to shortcut keys—often in an 'Options' or 'Settings' area. You can define a shortcut key for "Program Shortcut Key" to quickly open the Quick Settings dialog. The default shortcut to open the mini user interface under your mouse cursor is Ctrl+Shift+D.
If that didn't work: Other pre-defined shortcuts exist. Ctrl+Shift+Ins opens the attached DDM menu within a running application window. Ctrl+Shift+Home cycles between your 5 most recently used Easy Arrange layouts.
Heads up: You can also define shortcut keys for other functions: Easy Arrange MRU layouts, application window options for Auto Mode and Easy Arrange, and quick positioning for a PIP (Picture-in-Picture) window.