This means that instead of using the regular Google Site navigation, the pages are hidden and linked via a text menu. When you change a page link in the Pages Panel - you will need to update the link in the "hidden navigation" menu.
This can become a tedious process if you are not careful. I highly recommend considering which style of menu you want to use BEFORE attempting to change your web site or Page names.
Click on the hidden navigation menu and the menu should drop down (like image below). If you would like the menu to stay open while you make changes, be sure to switch the collapsible feature off.
be sure to switch the collapsible feature off.
NOTE: YOU MUST CLICK IN THE BODY OF THE MENU OR SELECT THE ICON TO OPEN THE COLLAPSIBLE MENU OPTION.
Select the page name you want to change. Select the pencil icon to open the change dialog box. Here you can update the link text or change the linked Page.
Note: This is not changing the name for SEO purposes! You will need to change the linked page in under the Pages Panel.
I would recommend changing the names of your pages inside of the Pages Panel before changing the links. This is because everything that is linked will remain intact. AKA the links will automatically update across your website.
But you will need to update the "hidden navigation" to include any new pages. You will also need to add any new pages to each "hidden navigation".
Open the Pages Panel and select the page you want to change the name of. Select Properties.
Here you can change the Page link name and set a custom path.
Here is an example of what the advanced custom path does.
My About page is names ABOUT | MEET CHELSEA but the advanced changes the actual link to https://www.shedesignsthings.com/about-chelsea-professional-web-designer
If you choose to not use the "hidden navigation" you have the option of creating a menu similar like mine. But you must also delete the hidden navigation on all pages. Or else your website will look odd. ~_~