With the In- Each Category based rule, you can provide discount based on the quantities purchased in a combination of Categories.

For Example: Buy 1 product from Category A + 1 product from Category B + 1 product from Category C give a 10% discount in the cart.

This will allow to get the discount of 10% only when the cart contains 1 product from each of the 3 categories A, B and C

Go to Cart Discount rules -> Create rule.

General tab:

Here comes the Condition tab, where to choose the category and the quantities as per your requirement.

Select the number of quantities in the cart at least -> value 1 ( which means 1 quantity from each category you select next)

In Each Category: Select the categories which you need to be combined to get the 10% discount.

Let see, how the discount looks in the cart:

Discount applies only when there are 1 product from each of the category.

The discount will only be applied to the Categories you are selected in the dropdown. So, when any other product from different category is added, that product alone will be exclude from the discount.

Similarly, you can provide various combinations with the in each condition in the cart based rule. To know more cart based rules -> (Click here)