You can detail both instance and layout-specific entities. However, some combinations can affect association; see Associativity for more information. Deleting a model mode entity that has an associated dimension attached in a layout instance, will leave the dimension in place, (delete manually if desired). Modifying a model mode entity that has an associated dimension attached in a layout instance, will update the dimension value:

 

NOTE: When dimensioning an entity that is tagged to an instance, the dimension will assume the instance scale. For instance, placing a 1" line in an instance scaled at 50% (and tagging it to the instance) will result in a dimension of 2.0" :