Invoke inspector update (from editorwindow)

I am trying to build an editor window to edit a node graph. All node data is contained in a scriptable object called "Project". There is a custom inspector for scriptable objects of type "Project", that works by recursivly exposing the project-object and some of its members.

Every other class i use is derived from System.Object instead of UnityEngine.Object, which means i can't use SerializedObject or SerializedProperty. (At least i think so - not sure if that matters.)

If a node in the EditorWindow is selected, i want to show only the node info in the inspector, instead of the whole project object. To do this, i have to somehow tell the inspector to repaint itself.

How would i achieve that?