Use a standard Advanced Discount Code on selected products or order subtotal (cannot target compare_at_price or customers)

Create an Advanced Discount Code that uses the Product Discount module (percentage or fixed amount) applied to the selected products/variants — or use an Order Discount (percentage/fixed) with an optional minimum purchase amount. Limitations: the discount will apply to the product's current price at checkout (there is no option to force it to apply against the compareatprice), and you cannot restrict the code to specific customer emails or auto-apply it. If you need the discount to effectively be calculated off the original price, consider adjusting product pricing externally (e.g., set the current price to the original value and use compareatprice for display) before issuing a standard discount code.