The mobile menu is displayed on devices with a screen width 760px or smaller.
You’ll find the Mobile Menu Link at the bottom of the menu.
As you’ve noticed, you can configure Mobile Menu Text and Link in Admin Panel > Themes > Custom Text and Links.
Most people will likely want to change “Your Custom Link” to their company name and link to their company website, but the choice is yours to make.
Thanks for asking, kkrumm. I’m going to have to add this to the FAQ!