Add text over the secondary navigation

You could add a phone number as an additional custom link menu item. In the url field you can add the phone number like this tel:12345678 with no spaces. Then in the link text field you can add the phone number with the proper spaces between the numbers.

This way the phone number will be clickable on smartphones.

Are is right - that's your best bet.

Then, if you want that item to be on the left side, you can give it a custom class (https://generatepress.com/knowledgebase/using-menus/#custom-classes).

With that class, add your CSS:

.your-chosen-class {
    float: left;
}

That should do it :)

Great Thanks!

You're welcome :)