DHTMLX Grid Sub rows

In version 5, we could create sub-rows for a DHTMLX Grid. That functionality no longer seems to be supported in Suite 6.0. Did I just miss the feature in the documentation?
Is there a plan to implement that feature in the future?
Is there an upgrade path between 5.2 and 6.x that might cover what features are no longer supported?

Unfortunately currently there are no subrows or subgrids in the dhtmlxGrid 6.
We have no plans to include such functionality in the near future.

Unfortunately there is no such upgrade path.

We absolutely need some solution to replace or use subgrid to move 5 to 6. Is this situation valid today that you don’t going to cover subgrid?

We have no plans to add the subgrid functionality to the dhtmlxGrid ion the near future.