В шаблонах core >global > forms > editorAttachments
Находишь строку
<a href='#' class='ipsButton ipsButton_light ipsButton_verySmall' data-ipsMenu id='elEditorAttach_media{expression="md5($editorName)"}'>{lang="editor_attach_other"} <i class='fa fa-caret-down'></i></a>
Перед ней вставляешь
<button onClick="javascript:window.open('http://yapx.ru','','location=0,status=0,scrollbars=1,width=960,height=660'); "class="Yapix"><i class="fa fa-file-image-o" aria-hidden="true"></i> Yapix</button>
<button onClick="javascript:window.open('https://imgur.com/upload','','location=0,status=0,scrollbars=1,width=960,height=660'); "class="imgur_com"><i class="fa fa-file-image-o" aria-hidden="true"></i> Imgur</button>
В custom.css добавить
.Yapix {
color: #f6f2f0;
background: linear-gradient(#5f4781 10%, #5f4781 90%) !important;
border: 0px;
border-radius: 3px;
width: 100px;
height: 30px;
}
.imgur_com {
color: #f6f2f0;
background: linear-gradient(#40098e 10%, #40098e 90%) !important;
border: 0px;
border-radius: 3px;
width: 100px;
height: 30px;
}