How to add template
First click on Products > All Products click in the screenshot below.
Select the template for the Single Upsell Product popup from here in the screenshot below.
Select the template for the Multiple Upsell Product popup from here in the screenshot below.
Note:- If you are adding variable product in upsells or cross-sells and you want to show single product then you should show this ‘Template – Variable Upsell’ template from ‘Template for single upsell product’ template select the as in the screenshot.
Note:- If you are adding a variable product to the upsells or cross-sells, and you want to show multiple products, then you can choose from ‘Template for multiple upsell products’ or ‘Template – Variable Upsells’ or ‘Template – Variable Upsells With Formatted Currency’ template select the as in the screenshot.