How do I set the default attributes for plots?

Each type of plot (Line, Scatter, Column, etc.) has its own layout that is stored as part of the Style file. Once you have a plot looking the way you want it, choose Plot > Define Layout. Once you click OK, KaleidaGraph will use the current layout when you create this same type of plot in the future. The layout remembers the position of the legend, type of legend frame, position and size of the axes, etc. This information also gets saved as part of the Style file when you quit.

This will not set defaults for any text labels. This must be done using the Text Options command.