[NTG-context] Defining mathsymbols from unicode char

Dear all, 1. I am trying to define the "pitchfork" unicode character( https://unicodeplus.com/U+22D4) to use in ConTeXt as stated on page 387 of new math manual authored by Hans and Mikael: \definemathsymbol[pitchfork][relation]["22D4] It works with some unicode characters and not others (like this character). What can I do to make it work? 2. I would like a \not\perp symbol but it doesn't draw the stroke on top of the symbol. I know you could manipulate this in a plain TeX but I am thinking the mechanism in ConTeXt would be different. How can I achieve this? Also how can I get the \notperp symbol in the accepted answer of https://tex.stackexchange.com/questions/27651/symbol-about-not-orthogonality... ? Thanks. Jethro