Using the View Filter you can make dimensions selectable or non-selectable.
To make dimensions selectable or non-selectable:
Select View
> View Filter or click the View Filter button on the Basic View
Control or Advanced View Control toolbar.
In the View Filter dialog, select the Notation tab.
In the Dimensions row, click the filter icon in the Selection column to toggle selectability on or off.
Dimensions are selectable
Dimensions are not selectable
Click OK.