toggle {<plotno> | "plottitle" | all}
This command has the same effect as left-clicking on the key entry for a plot
currently displayed by an interactive terminal (qt, wxt, x11). If the plot is
showing, it is toggled off; if it is currently hidden, it is toggled on.
toggle all acts on all active plots, equivalent to the hotkey "i".
toggle "title" requires an exact match to the plot title. toggle "ti*"
acts on the first plot whose title matches the characters before the final '*'.
If the current terminal is not interactive, the toggle command has no effect.