Create a new template with 'Is multi Variants' as True. In Variants tab, You will see Dimension types as one2many. Create dimension types like colour, size with appropriate value inside Dimension type forms like 'black', 'blue', 'M', 'L', etc. After adding this, click on Add All Option. You will see your all dimension values in Dimension Values field. Now, click on 'Generate Variants' button. It will create all the products as per your configuration in Dimension Types field. Overall, it means that with product_multi_variant, You can have many products per template. Hope this will help you.
Thanks,
Priyesh Solanki