Click on the layer list icon
to display the layer list or table of contents in your map viewer.

Clicking on the three dots
on the right side of a layer displays the layer menu, which includes the following functions:

Click on the icon
in the upper right corner of the layer list panel to control the behaviour of all layers. This gives you the ability to turn all layers on and off and expand or collapse all layers.

Click on the legend icon
to open the legend panel.
