Hi Marcin, you can use Snap [RMB] for that.
You can create the columns for the corner of the "stairs" (as I shown in the picture) and them use Snap again to fill the rows. Or, you can create a column to the center and a second for the corner and after you fill the between columns you can combine them (except the center one), duplicate it and use Flip [MMB] to fill the other half of the "stairs", Or ...
To create the rows you must to use elements of the seats for reference and target.
But, if you also need the seat to be rotated, then I would suggest you to try my Absolute->Rotate plugin.
You can create the columns for the corner of the "stairs" (as I shown in the picture) and them use Snap again to fill the rows. Or, you can create a column to the center and a second for the corner and after you fill the between columns you can combine them (except the center one), duplicate it and use Flip [MMB] to fill the other half of the "stairs", Or ...
To create the rows you must to use elements of the seats for reference and target.
But, if you also need the seat to be rotated, then I would suggest you to try my Absolute->Rotate plugin.