Hi,
Got yours, the icon is added using css, so you need to use the css class, I wrote the comment based on technical ground basis.
Here is the css that we used, you just need to override this.
.cbxwpbkmarktrig:before {
content: "";
margin-right: 3px;
vertical-align: middle;
background: no-repeat url('../img/bookmarkicons/bookmark_before_2x.png') 0 0;
background-size: cover;
width: 21px;
height: 21px;
display: inline-block;
}
.cbxwpbkmarktrig-marked:before {
background: no-repeat url('../img/bookmarkicons/bookmark_after_2x.png') 0 0;
background-size: cover;
}
If you are using pro addon there is more easy way to do this like adding icon in theme or child theme ‘s folder. screenshot for pro addon https://prntscr.com/sa7n9d