Heres a neat trick for your pre-holiday ARCHICAD-ing. In AC19 you may notice a lot of new pet palette options available when snapping on dimension elements.
One of these new options allows you to re-assign a dimension snap point by clicking on the dimensions tick mark hotspot. Click that point, then select this option from the pet palette:
Then just select the point you want to dimension to. The dimension string will now be dynamically linked to that new point; dimensions will be adjusted with the element’s changes.
This is also a great way to assign associations between dimensions and elements, if there previously was not one, or a way to change a dimensions association to a new element or point.