You can change all the parameters you selected while you created your scale. For a weight related scale, the most ‘frequent changes’ are adding a new range in your scale or modifying the upper limit of one of your existing ranges.
For a Tariff Zone related scale, the most ‘frequent changes’ are adding a new tariff zone, for this please assure you that the tariff zone you want to add if not already in your scale (you cannot duplicate values). For this, click on the yellow square ‘position’ in the Change scale: Overview screen.