If you want to prevent a rule from being used without deleting it, you can deactivate this rule, and reactivate it later when you need it again.
Choose the Apple menu > System Preferences, then click on Magic Launch.
Select a file type for the rule you want to deactivate in the list box of managed types on the left.
In the rule list box on the right, uncheck the on the check box beside the rule you want to deactivate.
Tip: You can deactiate all rules for a given file type at once by unchecking the “Use following rules” checkbox above the rule list box.
Choose the Apple menu > System Preferences, then click on Magic Launch.
Select a file type for the rule you want to activate in the list box of managed types on the left.
In the rule list box on the right, check the on the check box beside the rule you want to deactivate.