Convert expanded strokes back to live strokes
So far there is no way to de-expand strokes back to live strokes.
The suggested practice is to cut the shape in pieces and blend pairs with 1-step blends, expand and join manually — a tedious solution. We have to keep strokes alive as long as possible if we plan to edit them after. The effects we can use to make an art non-destructive are quite limited.
We now have cool Reform plugin by AstuteGraphics that allows to edit expanded strokes in a different way, but is does not solve the original problem and only helps to workaround and offers fluidity other tools don’t have... it can’t resurrect strokes.
Other solutions, in other apps, try to trace instead of reconstruct, and results are pretty poor most of the time.
Nicolas Gwinner commented
This can be useful if you want to remodify the size of a contour without redraw the shape.
I think that having the option to convert shapes to lines would be beneficial, especially if you're given line art to work on where the previous artist converted to outlines without saving a line segment copy (or if you forgot to do so). It could be simple, like just dropping a line segment spine in the center of the outlines.