Dear list 

With LMTX the Following MWE does not seem find attribute value (it does with luatex 1.10)

\defineattribute[MarginNode][public]
\newbox\MyBox

\startluacode
local nuts   = nodes.nuts
local margin_node_attr = attributes.public('MarginNode')

function test_attribute(box_id)
   local box = nuts.takebox(box_id)
   local margin_node = nuts.getattr(box, margin_node_attr)
   context('Expected 555=' .. (margin_node or '(nil)'))
end
\stopluacode

\starttext

Test.

\the\MarginNodeattribute

\setbox\MyBox\hbox attr\the\MarginNodeattribute=555{Test}

\ctxlua{test_attribute(\the\MyBox)}

\stoptext

Thanks