[whpalmer4]

Cmd-click on an item to toggle its inclusion in the selection. Sometimes it will be faster to click on one end of a range, shift-click on the other and then use cmd-click to remove the unwanted items rather than building up the selection one by one.

To quickly mark one or more items complete, select the row(s) and type option-+. If you are only selecting a single row, make sure you aren't in edit mode or it won't work -- the blue outline should include the row handle dot.

Thanks for asking this question, I'd never bothered figuring this out, but knew there must be a way! I'd always just used the inspector or the slider in the chart.