Feature Request: Subitems Progress have a Total Progress status at the bottom of the group

When you use Subitem Progress bars at the bottom roll up the sum of all the progress.

Additionally, it would be great to have all the column features that the items have in their groups such as the ability to select average or sums for number columns, and showing all the labels in a set of items.

How did you manage to make that sub-item progress from the parent item?