Here’s something I just learned and want to share with others and record for my use the next time I need to do this and have already forgotten!
The position and appearance of the figure legend in Maxima plots drawn with plot() (by setting gnuplot_preamble) and in draw() (by setting user_preamble), can be manipulated to any of the gnuplot options listed here.
Here are some examples:
The MaximaList 