Edit Bar controls: Parametric Dimension.
Change Status will switch the properties of a dimension from Parametric to Standard or vice versa.
A Parametric dimension will drive the size of the geometry it is set to whereas a Standard dimension has no such capability and will only display the size or entered text for the geometry it is to be notating.
To use, simply click the box on or off next to Parametric Dimension in the Edit Bar. Click on the dimension(s) you wish to apply the new property to.