As far as I understood Grid you are not able to add components inside Grid.
I don’t know why this setComponent() works. Please enhance your code by this:
I am actually doing the same thing… adding a Grid inside the HeaderRow cell of another grid. the Problem is that i dont see the content of the inner grid in the UI (even though it is in the DOM). is there a way to increase the height of that cell or get the inner grid on top or something?