Change all rows in an editable grid with same order no

Well, If I understood the problem correctly, this can be done within the saveInto attribute of the Order No column. Apparently, something like this

a!gridRowLayout(
            contents: {
              a!integerField(
                value: fv!item.order_No,
                saveInto: {
                  fv!item.order_No,
                  a!foreach(
                    local!items,
                    a!save(fv!item.order_No, save!value)
                  )
                }
              ),
             /*Rest of the code*/
        )

Here local!items hold the data and upon updation on Order No in any row, I am updating the entire data array's Order No to the latest entered Order No.

Hope this helps!