How to change the harvest level of vanilla Blocks or Tools?

You can't do anything that is related to Vanilla code

I am not a expert nor anything, but i think you can use a global value or something like that to change the values of the vanilla stuff without actually changing or modifying the original code. Iguana Tinker Tweaks do something like that so it's not impossible. Try to search on google or youtube, most people here (including me) are new to these stuff and don't exactly know how java works so yeah

hello new user!