How to create an aggregated 'average' row inside the table?

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Is there a way to 'insert' a row into the table data that provides the average value for a column across all rows?

I am able to do so using a function within the column Footer, similar to the approach laid out in #101, but it would be great to have a row that is rendered within the table, so that it can be sorted like any other row.

It seems like the other option is to use groupBy in order to run an 'average' aggregation on all the rows, but how could I make sure the aggregated row shows up below the original-data rows? Any time I have used an aggregate row, it seems to default to rendering above the original rows.

Thanks for your help!

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I see from #2510 that there may be some ability to control the placement of grouped rows coming in v8. Is there currently a way to control that placement, or place a grouped row sorted within a table?