\DeclareSymbolFont Not working with Ankiweb app


I am attempting to use math symbols that don't exist by default as part of existing packages in Options for notes (eg. amsmath). I tested the below code in TeXworks (pdfLaTeX) with no issues.

\DeclareSymbolFont{matha}{OML}{txmi}{m}{it}% txfonts

$ \varv = 0 $

Upon adding the \DeclareSymbolFont… to Tools => Manage Note Types => Options and inserting the above Declaration lines before \begin{document}, I tried below lines in Card
( \varv = 0 ) or [$] \varv = 0 [/$], but ankiweb app isnt converting this to symbol.

Is there something I need to do specifically? Or is the above steps not allowed in Ankiweb app.