[camster]

You can set the preference under the customer defaults
File - Utilities - customer defaults

Select the Assemblies section - Extras - You can use assembly constraints or Mating Conditions. I would suggest using Assembly constraints. You can convert your existing assemblly mating conditions to assembly constraints. they are not hard to use.
Read the help doc's

The best way to see the constraints is 1. Make sure the constraints display option is active on the assembly navigator. Right click in an empty area of the Assy Navigator and make sure the Include Constraints option is active. 2. When you select a component and want to see it's constraints expand the dependencies panel at the bottom of the navigator and click on details, the magnifying glass.