I'd like to add comment on this request, if I may. I think the custom graphs are the most useful, and by far the best looking charts of all the weather station software available at this time. JMHO.
I'm sure you've already thought this out, but just in case... my suggestion for a way to implement a user defined time range would be to maintain the predefined pop-up menu for "period:" as is, and add a pop-up for "minus:" with the same predefined choices as in the "period:" pop-up menu. The default value, of course, being zero and creating a chart in the same manner as it does now.
That way, one could fill a screen with scrolling charts displayed in multiple rows of the same parameters aging with each successive row. Example: 3 rows of 7 day charts, with the second row aged by 7 days and the third row aged by 14 days, producing 21 days total of highly detailed chart data. The boost in flexibility and granularity of data presentation would be huge, and would probably lead to a need for the ability to define chart groups for easy switching between sets of charts.
Best,
Herb
