How to SNAP top and down menu elements?

[listy]

Great, did some test using css calc and it works mush better, thanks.
I pushed it to the same test branch (4.8-sticky-headers)

Works as expected, will try it in prod.

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Tested in prod.
I think i had to add something to my custom layouts too, so it will not scrollable:

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Or, may be, same things must be added to CustomLayoutWdg too?