<span class="fr-marker" data-id="0" data-type="true" style="display: none; line-height: 0;"></span><span class="fr-marker" data-id="0" data-type="false" style="display: none; line-height: 0;"></span<span class="fr-marker" data-id="0" data-type="true" style="display: none; line-height: 0;"></span><span class="fr-marker" data-id="0" data-type="false" style="display: none; line-height: 0;"></span>If it is not possible to apply an additional discount in a sales order, it may not be set up. This can be set up through Extras -> Settings -> Promotions Section -> General Tab
'Never discount on discount' should be set to: No
Then an additional discount can be applied to the sales order.