You don't want admin.
Admin hacks are patched and impossible.
You want to trick the server to make it let you open mission editer.
You are an idiot. The server has no idea that you're trying to open the Mission Editor, because the Mission Editor is a client sided thing. The only thing preventing you from opening the Mission Editor is a check inside the editor's script to see if you're running the server. Delete that, and suddenly you can open it anywhere, but you can't actually do anything with it. This is because the Mission Editor relies on the fact that you are hosting the server, and the objects you try to manipulate exist on your computer. If you are connected to another server, the Mission Editor would not be able to do anything, because the objects you see are just ghosted from the server, so even if you could move your player around with it, the server wouldn't be informed that you did anything, and your player would teleport right back, because the mission editor is not designed to tell remote servers anything.