Yes, there is a way to exclude a category or SKU from existing Cart Price Rules without editing each rule individually. Here are the steps to do so:
Go to "Marketing" > "Promotions" > "Cart Price Rules" in the Magento admin panel.
Select the Cart Price Rule you want to modify and click on "Edit".
Scroll down to the "Conditions" section and click on the "+" button to add a new condition.
From the dropdown menu, select "Product Attribute Combination" or "Category" depending on what you want to exclude.
Select the operator as "is not" and select the category or SKU you want to exclude.
Save the rule.
Now, the Cart Price Rule will not apply to the excluded category or SKU. This method works for any Cart Price Rule, including those that are already created and active.