How to Enabling/Disabling a Discount Rule for Checkout
Click on the name of your conditional rule, look at the last option in the fee configuration form for the respective rule, and toggle the status bar to enable or disable it.
You can repeat the same procedure for all your conditional discount rules. Doing so will help you in managing the cart discounts well. Having the option for re-enabling these rules saves you from the extra work required to re-create the entire discount configuration again.
Please keep in mind that you cannot enable and disable the plugin through the plugin dashboard, and there is a reason behind that.
If allowed, many of your created rules will stop working all of sudden, creating errors for the checkout process. However, in case you actually do not want any of the discount rules to work for the cart, you can disable the plugin from the WordPress Dashboard > Plugins > All Plugins. There, you will find an option to disable the said plugin, just below the plugin’s name on the list. So, use it if essential.