To map Notes and Relations between Notes, you need a Sheet and that Sheet needs to be opened as a Sheet window. If you click any Note in the tree, a 'New Sheet' will be created automatically, if one does not exist yet, or has been renamed.
Notes are collected in the Sheet and the Sheet window from the project or knowledge base. You can create Relations on the Sheet windows only.
You can map From-Notes and To-Notes by dragging them directly from within the open Note, to the Sheet window.
Thus, while navigating your network, you can recollect related Notes and see if and how they are related, learn from it or update it for the next time you visit the node. You can roll out and visualize any critical path for and at any moment you need it.