OBJECT THAT INDICATES THE REFERENCE OF THE CENTER IN THE HEADER OR FOOTER
In Website X5 you can use an empty object (in my video I used the Text object) to extend to the width of each breakpoint to have the reference of the center of the Footer (or even of the Header, the procedure is the same) having as an indication the center of that same empty object. This indication of the center is useful for certain types of alignment: think of the alignment in the center of two objects placed horizontally next to each other instead of one above the other vertically (in the latter case you can use the "Arrange / Horizontal / Center Alignment ").

Watch this video tutorial: https://www.youtube.com/watch?v=sBD3hN7qBD0