The designer is hard to understand and manage to master it.
I tried to put a panel, then a many rows, add columns. But it seems to me that the designer proposes an adaptable model.
It takes a huge time and it is very hard to position elements on the design surface.
The designer does not show labels where the components / controls are.
I think it would be better to design in an absolute positional way and then that the tool proposes the transformation to an adaptable scheme as part of the code generation.
For now, you can consider documenting how to use the designer to position objects in the most efficient way possible.