Hey Ben,
Great question…this is a popular request, so it’s something that we’ve already finished up and included in our pending update. Unfortunately it isn’t an easy standalone addition because it doesn’t exist in the version of Font Awesome bundled with the theme, and the process of changing integrated FA versions is a bit of an ordeal (no fault of theirs, just the nature of it).
If the icon is worth a plugin though, you can get by in the meantime by installing the Font Awesome plugin and adding this CSS in the Customizer (or wherever you prefer):
.widget .menu-social-container .menu li a[href*="tiktok.com"]:before {
content: '\e07b';
}
