Can you add a command that you can give Items in a world.
also if you are in an other world? or not online?
(its because of my votier)

We need a command to edit Offline Player's inventories. Would be cool if the command would behave like the essentials /invsee , which opens the inventory to you, which you can edit freely in-game, and then it saves upon closing.

Maybe someday.

Since it's unlikely this will be implemented. You could use Essentials (EssentialsX is the updated version) or a plugin to /invsee. With modification permissions, you do just this.