Align right side of graphs (and left)

I have several graphs. (They happen to be box plots). Each graph has a legend. Each legend is a random width. I would like the graph area – the boxplot area – on each graph to have the exact same right and left locations, and width. The legends can be ragged, reflecting their random widths (though having everything line up nicely would be optimal.)

How do I do this? I can’t find plotly commands to freeze the width of the graph area irrespective of the legend width.