How do I make custom items for the offhand?

[LauchDerStarke]

How to make custom items for the offhand with special effects

[WorseKD1]

on load:
    set {custom.item.strength} to redstone dust named "&cStrength Talisman" with lore "&7Hold to get strenght 1 effect!"

every 2 seconds:
    loop all players:
        if off hand item of loop-player is {custom.item.strength}:
            apply potion of strength of tier 1 to the loop-player for 2 seconds

command /givetalisman:
    permission: op
    trigger:
        give player 1 of {custom.item.strength}
        send "&cYou have received strenght talisman" to player

this should work