This feature is still under development and will be available soon.
Upgrading can be very useful when you have too many NFTs not used to their full potential. This turns your current mining riginto ones with more hash power. This functionality is only available in your inventory.
How it works:
You can't upgrade the common and the uncommon mining rig but you can use them to upgrade other categories.
When you upgrade your mining rig it will gain more hash power.
Example: If you want to upgrade a Rare mining rig, you need to burn two of your Common mining rigs.