How can I achieve a tree-data layout with grouped rows?

[githorse]

I have a grid with several levels of grouping. I don't want each grouped level to appear as its own column, as it does in the demo -- this quickly gets unwieldy, IMO, with lots of groups. Instead, I want a more compact layout like this:

Specifically, I want:

1. The grouped columns to appear indented at a fixed (small) size, not as a full column width, so that they nest on top of each other but display the hierarchy visually; and
2. Each row to have an expand-collapse button to the left of the value (not in a single column to the right of all the groups, as it works in the demo.)

This "single group column" is the default in both AG Grid and MUI Datagrid. It's also essentially MRT's "tree data" view, but that view works with inherently hierarchical data, not flat data grouped by the grid itself.

How can I achieve the equivalent tree data / "single group column" style with MRT?

[githorse]

@KevinVandy any thoughts on whether this is possible? This one issue is keeping me from deploying MRT in my production app right now. It looks like the idea from the docs is to use getSubRows -- however, that means I would essentially be rewriting grouping and aggregating myself from scratch. Is there any way to make this layout work with the model's grouping state?