To hide the “All” option in the Glossary list, Please add this code to Custom JS field (the right textarea) in Content Views >> Settings page:
/* Glossary: Hide "All" filter option */
setTimeout(function(){
var $glsmenu = $('.pt-cv-gls-menu');
$glsmenu.children('li').eq(0).hide();
$glsmenu.children('li').eq(1).find('a').trigger('click');
},500);
Best regards,