Nevermind... I got it.

In the Menu Customizer, add the child page to the menu, then drag it underneath the parent page and to the right a bit. If you just drag it underneath the parent but don't indent to the right, the customizer doesn't recognize it as a child menu, but as a sibling.

I'm having the same issue. I have the Primas theme and it has an H1 element with class 'entry-title'.  It's wayyy too big at 41px. I've tried adding to the Customizer custom theme css and also the style.css:

h1.entry-title
{
    font-size: 20px;
}

That didn't work. 

Tried adding this to the config.php:

$boldgrid_framework_configs['customizer-options']['typography']['selectors']['h1.entry-title'] = array(
        'type' => 'subheadings', // also tried 'headings'
        'round' => 'floor',
        'amount' => .7,
    )

I can see that the style is being applied, but then overridden by this:

h1:not( .site-title ):not( .alt-font ), .h1 {
font-size: 41px;
text-transform: capitalize;
font-family: Raleway;
}

which is an in-page style in the header.... I can't find the source of what is injecting this style in the header. I've looked in the config, header and content files.

This is the in-page style element that is being applied:

<style id="boldgrid-custom-fonts" type="text/css">
        h1:not( .site-title ):not( .alt-font ), .h1{ font-size:41px; text-transform:capitalize; font-family:Raleway;}h2:not( .alt-font ), .h2{ font-size:28px; text-transform:capitalize; font-family:Raleway;}h3:not( .alt-font ):not( .site-description ), .h3{ font-size:28px; text-transform:capitalize; font-family:Raleway;}h4:not( .alt-font ), .h4{ font-size:20px; text-transform:capitalize; font-family:Raleway;}h5:not( .alt-font ), .h5{ font-size:16px; text-transform:capitalize; font-family:Raleway;}h6:not( .alt-font ), .h6{ font-size:14px; text-transform:capitalize; font-family:Raleway;}h1.alt-font, .h1.alt-font{ font-size:36px; text-transform:uppercase; font-family:Raleway;}h2.alt-font, .h2.alt-font{ font-size:30px; text-transform:uppercase; font-family:Raleway;}h3.alt-font, .h3.alt-font{ font-size:24px; text-transform:uppercase; font-family:Raleway;}h4.alt-font, .h4.alt-font{ font-size:18px; text-transform:uppercase; font-family:Raleway;}h5.alt-font, .h5.alt-font{ font-size:14px; text-transform:uppercase; font-family:Raleway;}h6.alt-font, .h6.alt-font{ font-size:12px; text-transform:uppercase; font-family:Raleway;}.wc-gallery .gallery-caption h2{ font-size:63px; text-transform:capitalize; font-family:Raleway;}.mod-gamma-1 h2, .entry-title{ font-size:16px; text-transform:capitalize; font-family:Raleway;}.page-template-page_home h2:not( .alt-font, .wc-gallery .gallery-caption h2 ), .page-template-page_home .h2{ font-size:22px; text-transform:capitalize; font-family:Raleway;}.p-button-primary a, .p-button-secondary a, .form-submit a, .ninja-forms-all-fields-wrap input.btn{ font-size:18px; text-transform:uppercase; font-family:Raleway;}h1.entry-title{ font-size:11px; text-transform:capitalize; font-family:Raleway;}.bg-font-family-menu { font-family: Oswald !important }.bg-font-family-body { font-family: Raleway !important }.bg-font-family-alt { font-family: Raleway !important }.bg-font-family-heading { font-family: Raleway !important }            blockquote, blockquote p, .mod-blockquote { font-size: 17.5px; }
        </style>

Are we being forced to use !important?