[Solved] How to target player's main hand

Im adding a multi tool that changes depending on what block you're mining.
Theres 4 states : axe, pickaxe, shovel and hoe, which are actually 4 different items.

Whenever you right click a block, it transforms into the right tool to mine it.
The problem is you can't add 1 item to the main hand of the player. You have to tell the slot numer.

So if you know any way to add an item to the slot that is currently the main hand, help me, i need help

[Later edit] : I found out there was a "set item in main hand of entity to ""  " i just didn"t see it. If i could i would have deleted this topic.