If you want to change this icon from Mobile Menu:

Replace the icon with custom css through WpRentals Child theme -> Style.css

Install Child theme -> Edit Style.css and copy paste below code

Help to install child theme https://help.wprentals.org/article/how-to-activate-child-theme/

i.fas.fa-cogs {
margin: 25px 0px;
}

.mobile-trigger-user:before {
content: "\f007";
font: normal normal normal 14px/1 FontAwesome;
font-size: 30px;
}

.fa-cogs:before{
display:none;
}

Clear theme cache (if enabled)

Clear browser cache if needed (mobile browser cache too)

Check results