LegendLabel

is an option for legends that specifies an overall label for a legend.

Details

LegendLabel->None specifies that no label should be given.
LegendLabel->Placed[lbl,pos,fun] puts lbl with fun applied at the position specified by pos.
When the label position is Bottom, Top, Left, or Right, the label will be inside any structure created by LegendFunction.
When the label position is Below, Above, Before, or After, the label will be outside any structure created by LegendFunction.

Use no label:

Use any Wolfram Language notation for labels:

Place the label below the legends:

The label is inside the wrapper function specified by LegendFunction:

Place the label outside of LegendFunction:

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