Hello @Jankko ,
I understand you are looking to remove the underline on the navigation menu when users hover over submenu items or active page menu items.
To remove the underline, in the hover submenu case, you can use the below-mentioned code.
→ Add the code at the bottom of the theme.liquid file before tag and save.
In another issue, please use this code -
I hope the code helps you.
Thank you.