Adding an item to the item updater

1. Enter the command area behind the item updater. Make sure to replace blocks broken and block access again once you are inside.
2. Create a copy of the command block. There is a labelled chest containing a command block with all the things you need, but blank for the item id areas. 
3. Place it next in the chain. Your command block should follow the last one, which should be labelled with a birch sign saying what item it updates.
4. Hold the non-updated item. Ensure you are only holding one of the items in your hand, as the number of items carries over.
5. Get the item data. Make sure your logs are open, then type and run the command /data get entity @s SelectedItem and copy everything from the open curly brace to the closed curly brace (these guys -> {}).
6. Paste the data. Insert it in the empty square brackets near the top. 
7. Hold the updated item. Repeat step 5 with the new item, again making sure you are only holding one.
8. Paste the new item data. This time you’ll paste it after “set value” in the command block.
9. Label it. Place a birch sign above the command block that communicates what item it updates.
10. Test it. Make sure to throw the item into the hopper outside to make sure it works. Once you’ve confirmed that, you’re finished!