Help Centering Navigation w/out Stacking

Site URL: https://turkey-rhino-4s9a.squarespace.com/config/

Hello!

I need help centering my navigation in one line between my logo (left) and donate button (right). Basically the way it looks now, but with the one-line navigation bumped to the center rather than right-justified.

I've seen this asked a lot, but haven't found a piece of code that works on my site yet. Please help!

Thank you!

https://turkey-rhino-4s9a.squarespace.com/config/ 

Add to Design > Custom CSS

nav.header-nav-list {
    flex-wrap: nowrap;
}