I ran into this recently via a customer request. They wanted to suppress all sketch relations on certain sketches.
First, go to the Sketch tab in the Command Manager, click on the Display/Delete Relations.
Then go to the Relations dialogue box and Shift + select all your sketch relations, then check the Suppress check box.
Notice below how the suppressed relations are been grayed out.
Note: If you have configurations, you can specify which configuration(s) your relations will now be suppressed. See below:
Check you later!
Sr. Application Engineer