weird icons on the sticky menu

Hello,

Thanks for the great plugin! There is one thing it is bugging me. The expand sign on the menu originally looked like an arrow “>”. Since I applied the sticky feature, that sign became a square box on the desktop and a box with an “x” on the mobile version… Do you have any chance how to modify that ugly sign to the previous one or a nicer one?

Looking forward to hearing from You!

Thanks!

The page I need help with: [log in to see the link]