To disable a gear rule, open the Gear Rules window from the panel on the left of the Dashboard. You will see a toggle button to the right of each rule. Moving the button to the left disables the rule so that it will not be automatically triggered.
You will be able to see that the rule is disabled in the main 'Gear Rules' window from the button position and because the text is gray'd out. In the image below, the "Create Nifti" rule is disabled.
The ability to disable a rule can come in handy if you have a new version of a gear that you would like to run on your data, but do not want to delete your old gear rule for the older version.