WP File Manager

Name	Action
..
block.json	Edit
editor-rtl.css	Edit
editor-rtl.min.css	Edit
editor.css	Edit
editor.min.css	Edit
style-rtl.css	Edit
style-rtl.min.css	Edit
style.css	Edit
style.min.css	Edit

Editing: style.min.css

.wp-block-navigation .wp-block-page-list{align-items:var(--navigation-layout-align,initial);background-color:inherit;display:flex;flex-direction:var(--navigation-layout-direction,initial);flex-wrap:var(--navigation-layout-wrap,wrap);justify-content:var(--navigation-layout-justify,initial)}.wp-block-navigation .wp-block-navigation-item{background-color:inherit}