Choose the graphs you want to be displayed in the third section of the Plot Context Menu.

Clicking Toggle Visibility deactivates or activates the visibility of all the graphs in the plot at once.

Unchecking one of the entries deactivates the visibility of this particular graph in the plot visualization. It is also removed from the legend.

If the plot contains many graphs (16 or more), the visibility settings cannot be done in the Plot Context Menu anymore. Instead, they you have to use the Edit Graph Styles dialog.