NBT tags for items not sync with server

Hey , its been a while :)

I still have a problem with the NBT Tags. I understand that instead of using NBT tags for players, it´s better to use global variables like player_persistent.

But in my case I give a nonstackable item some NBT tags because this item is supposed to store certain information. (no player should have these information, only the item - respectively the player transfers these information onto the item so the player doesnt have them anymore).

The problem on multiplayer here, however, is that it is still not synchronized with the server. Is there a way to bypass this?

Something like a global Item_persistent variable xD ?

It would help me very much! Thank you! <3