How can I edit the mobile menu without changing the PC version?

Hi Bonhamwest
In this case please do follow steps below:
Step 1: You have to uncheck Mobile Menu option at the dashboard>>Appearance>>Menus>>Primary Menu-Tool>>Menu Settings>>Display location before
Step 2: You have to create a new menu also and check Mobile Menu option again.
Hope it useful for you
REgards,
Maason