The Nodes Menu is accessible only in creation/editing mode.
Align Beginning to Previous Object moves the beginning of an edited object to the end of previous object.
The next command, Align End to Next Object, causes the end of the object being edited to the beginning of the next object.
Align Line Beginning to beginning of Previous. When doing a complex line, some line parts start not on end of previous part, but on its beginning, instead. Use this function to place beginning of the new part exactly on beginning of previous part.
Reverse Nodes Order changes the order of nodes.
Use Delete Whole Edge command to erase whole edge and start its creation anew.
Snap nodes to Work Area Edges, Snap to Guide Lines, Snap to Nodes, Snap to Object Edges are options for alignment of nodes during editing or creation of object. Nodes are snapped only if they are moved near to the work area edges, guide lines, other nodes or edges of other objects, respectively.
Please note: these options affect snapping of the edited nodes. Snap options under the main menu > Edit affect snapping of the whole objects.
Snap to Nearest Node command moves selected node on top of nearest node which belongs to other object. It means that it does not snap selected node to nodes of actually edited object, only to nodes of other objects. This command helps to align nodes (for example road intersections) precisely.
Select First Node, Select Last Node commands select respective node on the vector edge. These commands help to locate first and last node on complex edges with large number of nodes.
Select Previous Node, Select Next Node commands switch selection to previous or next node on the vector edge. These commands, however, are supposed to be used with short-cut keys, not via this menu.