D365FO: Hierarchical Grid Common in form ProjWorkBreakdownStructure / extension?

Hi,

I was unable to find any proper documentation of the Hierachical Grid Common control which is used e.g. in form ProjWorkBreakdownStructure (Project management and accounting -> All projects --> PLAN -> Activities -> Work breakdown structure).

We've got requirements to add fields to the grid, but the grid seems to be totally dynamic, the columns are handled in JavaScript (WBSSchedulePlanningView.js row 1273) and there are no direct datasources on the form. Btw, our client is on 1611PU5 at the moment.

Is there any possibility to extend this grid using purely extensions? If not, is there any documentation how to code the grid? Using normal form grid we seemd to have much better tools to use the grid.

Any ideas?