The easy way

In the menu, add this as the navigation label

<span class="hws_menu_cta">Book now</span>Code language: HTML, XML (xml)

And add this to the custom CSS

/* -- START menu item CTA -- */ 
.hws_menu_cta {
background: #8C734A;
color: #ffffff;
padding: 7.5px;
}
.hws_menu_cta:before {
content: "\e023";
font-family: 'ETmodules' !important;
padding-right:3px;
}
/* -- END menu item CTA -- */Code language: CSS (css)

Josh Hall’s way

Primary menu, rounded corners

Source: https://joshhall.co/how-to-create-call-action-button-for-the-divi-menu/

/*---------------Menu CTA Button---------------*/
             
.menu-cta a {
    border: 2px solid #ffffff4f!important;
    padding: 12px!important;
    border-radius: 25px;
    text-align: center;
}
 
.menu-cta a:hover {
    background-color: #8dc63f;
    color: white!important;
}
 
.et_header_style_left #et-top-navigation {
    padding-top: 16px;
}
 
.et_header_style_left .et-fixed-header #et-top-navigation {
    padding-top: 6px;
}
 
/*---------------Menu CTA Button Mobile Settings---------------*/
 
@media only screen and (max-width: 980px) {
.menu-cta a {
    background-color: #8dc63f;
    }
}Code language: CSS (css)

Geno’s way

Sources

• https://www.facebook.com/groups/DiviThemeUsers/permalink/781588078637457
• https://quiroz.co/transform-a-divi-menu-item-into-a-cta

In the menu, add this as the navigation label

<span class="et_pb_more_button et_pb_button">Button Text</span>Code language: HTML, XML (xml)

This follows the default button styling from the theme customizer. To change that, add this to the custom CSS and change where needed

/* -- START Menu CTA Button -- */
#et-top-navigation .et_pb_button {
    margin-top: 0px;
    font-size: inherit;
    font-weight: inherit;
    color: #007000  !important;
    background: #FDFCFC !important;
    border: 2px solid #007000 !important;
}

#et-top-navigation .et_pb_button:hover {
    color: #007000 !important;
    border: 2px solid #007000 !important;
}
 
#et-top-navigation .et_pb_button:after {
    font-size: 23px;
}
/* -- END Menu CTA Button -- */Code language: CSS (css)