Is it possible in any of the available editors to select a node and then split all ways that cross it in a single operation? The split command in JOSM (shortcut P) requires repeating the operation for each way individually. I know that the turnrestrictions plug-in can do that for a pair of ways, but I’d need to do it for intersections of multiple ways (sometimes dozens) to accelerate my work.

I’m doing a manual import of overlapping bus routes (each route is a single way as member of a route relation) and I’ve discovered that the conflation plug-in can assign relations correctly to existing streets as long as the new routes and the existing streets are split at nearly matching points.

H, in JOSM “Unglue Ways” from the tools menu unglues all ways in one click, the nodes are then depicted as small squares on top of each other. You then unpick the pile one node/way at a time. I use this method to find single nodes at an intersection, unglue, then unpick the pile till the unconnected single node is found, (delete it) and reposition the way end nodes and merge them back together again.
Bernard

Fancy Geometry item 3
Want to disentangle two or more ways that share the same node? Highlight the node and press “G”, the shortcut for the unGroup built-in.

You'll get lots of copies of the original node all in the same place. Be sure to merge any unwanted ones back together.
If you also select one of the ways which share the node(s) before unGrouping, then after the unGroup the selection will be replaced with one containing just the copies which ended up in the way you selected.