To add/remove a witness line from a multi-segmented dimension, you click Edit Witness Lines and select the reference you wish to add/remove.

To change a witness line in a multi-segmented dimension, you select the dimension and click on the Move Witness Lines control of the reference.

To change a witness line in a multi-segmented dimension, you click Edit Witness Lines to select the existing reference and select the new reference.

To change a witness line in a multi-segmented dimension, you click Edit Witness Lines to select the existing reference and drag it to a new position.