To add a title text under Logo, you can follow these steps
#1. Access Settings
#2. On the left side of the screen, scroll down to the Advanced section and select Code Injection. Next, click on Edit.
#3. Paste the below code to Code Injection (Site header)
<style>
a.gh-navigation-logo:after {
content: "enter site title";
font-weight: 300;
font-size: 20px;
}
</style>
#4. Result