Lets get this clear, I have no idea of how to code anything, but i have messed around with this plugin. And I've noticed that when I try to edit an item I'm holding on any of my friend's severs, it doesn't work.
Is there a way this could operate on only the client side? If not or if that would require remaking everything then I'm totally fine.
just curious.

it's a mod, not a plugin

The only feature that would work on a non-modded server is updating an item that is in your inventory if you're in creative mode. Doing anything else would require tinkering with commands / command blocks (which would also require you to be an operator on the server), and it is quite a lot of work to do, but it's something that I have in mind.