Hi Aaron,

The very top of Employee center is coming from "Employee center Header" record in "sp_header_footer" table.
The "My request" menu is hardcoded in this record.

One way is:
You can create a Menu in "sp_rectangle_menu_item" table with Parent menu = "Employee Center Menu", Type=page and Page="<your page>".
Then you can create a new Menu item inside Advanced portal navigation record and map above menu item. It would appear with taxonomy in second row of Employee center header. You can refer below screenshots.