Click the 'Toggle Stand Dims' button which is located on the HOME ribbon or, if stands have been selected then click on the little arrow underneath the Tidy Dimensions button which will be located on the Dynamic ribbon that appears when stands are selected.
TIP: You can also initiate this function by using the default Hot Key ' D '
Now just hover over a Stand Dimension or in the space where a Stand Dimension should be (which is in the middle of a stand edge) and a little circle with a cross in it will appear, then just click. The dimension will then be added or removed accordingly.