The mod Adventurer's Toolbox adds tools that use the same item id based on type and are differentiated based on specific NBT tags. It is impossible to change the harvest level of one tool of a certain material.

Relevant link: https://github.com/the-realest-stu/Adventurers-Toolbox

The harvest levels for every material is specified within the first variable number here:

public static final HeadMaterial HEAD_WOOD = new HeadMaterial("wood", 0, 59, 2.0F, 0.0F, 15,

https://github.com/the-realest-stu/Adventurers-Toolbox/blob/master/src/main/java/toolbox/common/materials/ModMaterials.java

Thank you for considering!