Custom Editor Window size

Hey, all, RiokuTheSlayer here again.

Just wonder, in a custom UI window, is there a way to make a certain thing like a GUI.box scale with the window?

Here’s what I have:

void OnGUI(){

        if(treeObj==null){
            treeObj = (GameObject)EditorGUILayout.ObjectField(treeObj,typeof(GameObject),true);
            if(tree==null && treeObj != null){
                tree=treeObj.GetComponent<ConversationTree>();
            }
        } else {
            Rect box = new Rect(10,10,50,50); //This should be the rectangle of the window, with some minor changes I'll make myself to make it fit how I like

            GUI.Box (box, "");
        }

        if(GUILayout.Button("Remove object"))
            treeObj=null;//This is in case I make any changes to the object or need a new one to edit.

    }

If you see anything else I can change, feel free to say! I’ll be happy to take any advice on custom windows, never done it.

Also, if anyone knows a way to have some rects I can drag when the mouse is clicked over them? I’m trying to make an editor like the Animator one they have, where you can link up different things together.