Click on the Preferences tab in Settings. The view lists the last selected dataset and background layer.
To reset the preferences, click on the Reset Preferences button 
.
The preferences storage is not cross-browsers compatible. In fact they are stored in the local storage of the browser and thus they are not cross browsers compatible.
Click on the layer Manager tab in Settings, the view displays the layer manager form.
You can add your own WMS or WMTS layer or server by clicking the "Add layer" button.
When you tick on a layer name or list, it will be automatically added in your layer list that you can then manage here Section 2.3.4, “Map Overlay Layers”.
You can remove a layer or a list of layer by clicking on the "x" button when your mouse is on this layer name or list.