A belated thanks to EIB. Unfortunately, the Score > Settings dialog box, while rich in features, doesn't address system margins.
Currently, to change a system margin, one must right click on a staff, select System Margins, then right click on System Margins, where I change it from the system default of .55 inches on either side to 1 inch on either side. All well and good, but when I go to the next line, the margins revert to the system default. So I end up having to stop each time I go to a new line and change the system margins again. This recurs for each line on my score. It seems as if this is something that should be addressed as a default setting so my transcription process isn't interrupted each time I go to a new line.