extending a node (multi)selection

[A_Pirard]

When trying to detach a long multi-polygon or something from a road, or whatever the reason to have to select a long series of contiguous nodes, e.g. to duplicate and to move aside, the temptation is high to use the conventional method: shift-click.
It does not work, alas. It could, however, as follows.
Basically, shift-click only duplicates what can already be done with control-click.

1) to simplify the logic, and to keep shift-click mostly compatible if needed, possibly request to preselect (and later unselect) the way(s) over which the nodes to select will extend [this option inside brackets...]
2) when a node [on a selected way] is shift-clicked, follow the [selected] ways in all directions [, rejecting meshed selections (junctions of more than 2 ways),] and count the nodes until a selected node or the initial node is met
3) choose the path with the lowest count and select the nodes on it

Very useful, simple enough I think, and fun to program I guess, alas, I'm unable to.