If there was a part that was created on a local script in the client, would there be some way to give the part to the server so that server scripts could edit the part? And how could I do it? I've tried using remote events but it only comes as nil.
No. That's not possible.
A Local Part is inaccessible from the server, it doesn't exist. It does only on your client.
Imagine I have an imaginary friend I made up, and real people (the server, for example) can't actually talk to it or do anything with it.