That first line after BEGIN_PGML works perfectly to hide MathView in cases where it shouldn't be there. Thanks for this.
Any thoughts on how to get it to work with older problems written in PG?
I experimented with adding the same line after BEGIN_TEXT in a true/false problem written in PG. It disables the button, but it also leaves an artifact in the text of the problem. (Part of the code remains visible.)
Probably the right answer is to use PGML exclusively. But there are some good matrix problems in the OPL that would take some work to convert.