remove page from drop menu on mobile

Site URL: https://www.trevoarquitectos.com/

Hi, to add aditional images to the index page without having more actual pages in menu i used this code:

ul.folder-child [href="/cover1"] {
    display: none !important;
}
ul.folder-child [href="/cover2"] {
    display: none !important;
}
ul.folder-child [href="/cover3"] {
    display: none !important;
}

the problem is that this doesn't hide in the mobile version menu, any ideas?

Add to Home > Design > Custom CSS

li.page-collection {
	[href="/cover1"] {
    display: none !important;
}
[href="/cover2"] {
    display: none !important;
}
[href="/cover3"] {
    display: none !important;
}
}

thanks!