This is a Cart based discount rule to consider the Number of individual products are in Cart as a Condition to apply discounts.
Each individual products are considered as a line item in the cart. However, when you have variable products, each variable will be considered as a separate product as per woo-commerce.
Let us see, how to set up discounts based on the line items in the cart:
Example Scenarios:
20% discount when cart has more than 3 different products. (Count all items in the cart)
20% discount when cart has more than 3 different products from the specific category. (Only count items chosen in the filter sets for this rule)
To create such rules,
Go to WooCommerce -> Woo Discount Rules -> Add new Rule :

Scenario 1 :
20% discount when cart has more than 3 different products. (Count all items in the cart)

Here is a screenshot of how the cart page looks with discount applied :

Scenario 2 :
20% discount when cart has more than 3 different products from the specific category. (Only count items chosen in the filter sets for this rule)

Here is a screenshot of how the cart page looks with discount applied :

The discount applies only when 3 different products are in cart from the specified Category.
Video:
Still, unclear ?
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