dragging folder block not working in FF 23 (on Win7 x64) neither FF x64 Nightly Rated 5 out of 5 stars

most of 6.12 now working in FF 23 and Nightly x64
But unfortunately Not:
'modify layout with dragging folder block'
(works in 1st Column)

('modify position of a bookmark item with dragging link', does work)
could you please have a look at this

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