Hello,

You can add in the following custom CSS in your Admin Dashboard > Appearance > Customize > Theme Options > Advanced Options > Custom CSS field

@media(min-width: 769px) {
.main-navigation ul li li.menu-item-has-children > a::after, .main-navigation ul li li.page_item_has_children > a::after {
    top: 4px;
}

.main-navigation ul ul a {
    padding: 4px 7px;
}

.main-navigation ul li a {
    padding: 5px 12px;
}

.main-navigation ul li.menu-item-has-children > a::after, .main-navigation ul li.page_item_has_children > a::after {
    right: 14px;
    top: 6px;
}

.main-navigation ul ul {
    top: 34px;

}
}

This will decrease the padding and spacing provided to the menu items initially by the theme making it sleek and should allow you some extra spaces for some extra tabs in the main navigation on desktop screens.

Hope this Helps,

Best Regards !!