I would like to adjust a rudimentary drawn area (neighborhood) so that it uses the same nodes as the nearby streets. Doing it by hand seems very combersome - I use "a" or a nearby plus symbol to create a new node on the way, then I select it, and shift+select nearby street node, and hit "m" (merge). How do I select "bad" line, and make it auto-join all the nearby nodes along the way, possibly with clicks or a keystroke. I know about "follow", but that only works for a new drawing.
JOSM has a follow mode. Draw your way by using two consecutive nodes of an existing way, then just repeatedly press f to follow this way.
However most OSM editors are against joining highways with areas. Therefore I suggest to draw the neighborhood area completely separate instead of re-using nodes from the street.
Beware is it very powerful.