I'd be great if we could have an option in the config to set how many times the Tool Belt can be upgraded. I am personally looking at limiting the belt to a max of 6 slots, but I know some people have been asking for more if possible. Having an option for something in a range (say [0-9]) would be a much appreciated config option.
To go along with that, you might be able to put in a config for xp cost to upgrade each level in the anvil, or possibly easier, a starting level amount and the increase value for each upgrade.

Thank you for your work on this great mod!