themes-wordpress/varia/sass/components/header/_site-mobile-nav-side.scss

$wpcom-marketing-bar--height: 45px;
$wpadmin-bar--height: 46px;

// Updates the Mobile Navigation to be next to the site title.
@include media(mobile-only) {
	.mobile-nav-side {
		.has-menu {
			&:before,
			&:after {
				content: none;
			}
			position: relative;
			display: grid;
			grid-gap: 2px;
			grid-template-areas: 
				"site-logo site-logo" 
				"social-navigation main-navigation";

			&.has-title-and-tagline {
				grid-template-areas: 
					"site-logo site-logo" 
					"site-title main-navigation" 
					"site-description main-navigation" 
					"social-navigation social-navigation";

				.site-title {
					grid-area: site-title;
					align-self: end;
				}

				.site-description {
					grid-area: site-description;
					align-self: start;
				}
			}

			& > *:not(.site-logo) {
				margin: 0;
			}

			.site-logo {
				grid-area: site-logo;
				justify-self: center;
				margin: $baseline-unit 0;
			}

			.social-navigation {
				grid-area: social-navigation;
				align-self: center;
			}

			.main-navigation {
				grid-area: main-navigation;
			}
		}

		.site-header #site-navigation.main-navigation {
			margin: 0;
			justify-self: end;
			display: flex;
			align-items: flex-start;
			justify-content: end;

			#woocommerce-toggle,
			#toggle {
				&:checked + label{
					position: fixed;
					top: 2 * $baseline-unit + 2px;
					right: 2 * $baseline-unit;
					z-index: 20000;
					margin-right: 0;
				}
			}

			#toggle-menu {
				order: 2;
				grid-area: menu-toggle;
			}

			#toggle-cart[for="woocommerce-toggle"] {
				order: 1;
				grid-area: cart-toggle;
				margin-right: $baseline-unit;
			}

			#toggle-cart[for="woocommerce-toggle"].button,
			#toggle-menu {
				line-height: 1.55;
				padding: (1.5 * $baseline-unit);
				display: inline-block;
				text-align: center;
				justify-self: end;
				font-size: #{map-deep-get($config-global, "font", "size", "xs" )};
			}
			#toggle-cart[for="woocommerce-toggle"].button svg {
				margin-top: -2px;
			}
			.woocommerce-menu-container,
			& > div {
				grid-area: dropdown-menu;
				margin-top: 2 * $baseline-unit;
				position: fixed;
				z-index: 100;
				top: 0;
				bottom: 0;
				right: 0;
				left: 0;
				background: #{map-deep-get($config-global, "color", "background", "default") };
				padding: (6 * $baseline-unit) (2 * $baseline-unit) $baseline-unit;
				overflow-y: auto;
				white-space: normal;
			}

		}
		&.has-marketing-bar {
			//Consider marketing bar height
			.site-header #site-navigation.main-navigation > div{
				top: $wpcom-marketing-bar--height;
			}
			.site-header #site-navigation.main-navigation {
				#woocommerce-toggle:checked + label,
				#toggle:checked + label {
					top: (2 * $baseline-unit) + $wpcom-marketing-bar--height;
				}
			}
		}

		&.admin-bar {
			//Consider admin bar height
			.site-header #site-navigation.main-navigation > div{
				top: $wpadmin-bar--height;
			}
			.site-header #site-navigation.main-navigation {
				#woocommerce-toggle:checked + label,
				#toggle:checked + label {
					top: (2 * $baseline-unit) + $wpadmin-bar--height + 2;
				}
			}
		}

		&.admin-bar.has-marketing-bar {
			// Consider admin bar height + marketing bar height
			.site-header #site-navigation.main-navigation > div {
				top: $wpadmin-bar--height + $wpcom-marketing-bar--height;
			}
			.site-header #site-navigation.main-navigation {
				#woocommerce-toggle:checked + label,
				#toggle:checked + label {
					top: (2 * $baseline-unit) + $wpadmin-bar--height + $wpcom-marketing-bar--height;
				}
			}
		}
	}

	// Keep the menu pinned to the top when the menu is open.
	.lock-scrolling .site {
		left: 0;
		max-width: 100%;
		position: fixed;
		right: 0;
	}

}