Specify the units to move and steps not only pixels

Sometimes it is necessary to move the objects a fixed distance regardless of the zoom of the screen. For example, in electronic design is normal a grid of 2.54 mm. In these cases (after defining the units of the grid) would be interesting to choose the units of displacement (in spanish: Archivo/Preferencias_de_Inkscape/Desplazamiento; Archivo/Preferencias_de_Inkscape/Pasos). Currently it is necessary to write and erase (+ and -) every time in the text boxes the amount of displacement.