How to make a tool keep its enchants when upgraded in smithing table

I have made a smithing template to upgrade netherite tools to a higher tier, but when upgrading in the smithing table it doesn't carry over any enchants of the base item. How can i apply the enchantments of the base item to the upgraded item like it is when upgrading from diamond to netherite in vanilla? Some other posts said to use "procedures" but they weren't really detailed. As i am new to modding please try to explain in basic terms for me to understand.