I rigged a venetian blind this way.  The main trick in the blinds is to use the same deltaAddDelta in each slat, and a slightly different Max Y. All the slats are childs of the bottom bar; when you pull up the bottom bar, each slat moves linearly upward with the bottom bar until it reaches its own Max.  It then stops while the slats below continue moving up.

The result is a neatly spaced pile of slats.

(I think this description is sort of backwards, but trying to parse it out
again would give me a headache.)

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