The CSS in the
<head> is controlled by the Customizer settings.
There’s no way to have the options write CSS that ends up in a separate file without being hacky.
With that being said, Google Page Speed tests actually recommend adding your CSS inline in the
<head> – it gives better page scores.
Changing the height of your menu items can be achieved using the Spacing add-on – changing the values in that add-on will adjust the CSS in the
If you’re not interested in the add-ons, you can use my Simple CSS plugin to add your CSS, which shows up below the other CSS, meaning it will overwrite anything above it: https://wordpress.org/plugins/simple-css/
Let me know if you need more info 🙂