WordPress Multisite global menu tips: create, display, customize

display it in any place and customize

You’ve created a navigation menu on the main site. Let’s see how to make it work across all websites of the network.

How to make sub-sites which use the same theme inherit navigation menu from the main site?

I’ll use Twenty Seventeen Theme  as an example, but this can be done for any other theme and any other template file as well.
Here is the default footer.php content