Currently, it doesn't look like it is possible to set goals to show on existing reports.
My current insights dashboard is set up in columns, using Reports.
Column 1 is data for a set period, shown by quarter.
Column 2 is data for the same period, shown by month.
If I could just tick 'show goals' on those reports it would save a lot of time. The way Goals is set up currently, I have to recreate all of my existing reports. I would also need to duplicate several goals to be able to show the data by different intervals (i.e. monthly/quarterly).
It would also give more flexibility because there are more ways to show the data in reports than there are in the current goals feature. At the moment, goals data is shown by bar graph only (as far as I can tell).