Hi Chris,
Maybe I misread the OP's question, but I took "enable JavaScript" to
mean get JavaScript to run within BlueGriffon - and the answer to that
is you can't. You can't be more helpful than that in response to the
question asked. Perhaps I should have mentioned that that is why there
is a "Preview in Browser" button on the toolbar. Apologies to the OP
if that lack of completeness appeared unfriendly.
I accept that I did fail to interpret the question as one asking "How
do I enter JavaScript" which is the question your link answers.