no answer on forum so looks its improvement idea.
https://groups.google.com/forum/#!searchin/idempiere/context$20help/idempiere/bx_WnYJKjIE/6VDliszzVzwJ

User Story: As client admin want to improve users knowledge transfer by adding context helps and attach them to window customisation Window/Tab/Field level.

THEN power users (client admin) should able to enable contextual helps for his users various way. (make an accurate contextual help about business processes etc.)

norbert