How to change maximum item durability in Minecraft?(No Enchantment)
Solution 1:
You can use the NBT tag, Damage to give you an item with damage on it. Since a diamond pickaxe has 1561 durability, the command /give @p diamond_pickaxe{Damage:50} would give you a diamond pickaxe with 1511 durability left.
If you wish to change the durability of an existing item, you can use /data merge entity @e[type=item,distance=..3,limit=1] {Item:{tag:{Damage:0}}} to set the durability of an item that is dropped on the ground