If you want to add a custom link in a “Heading or HTML” area, add this link like this:
<a href="javascript:" onclick="myOpenInDlgFunc('/DFFS/Lists/Tasks/DispForm.aspx?ID=107')">This is my link</a>
Add this to the Custom JS textarea in the “Field table, Custom JS and CSS” tab:
function myOpenInDlgFunc(url){
OpenPopUpPage(url,function(result){
if(result === 1){
// dialog is closed with OK
}else{
// dialog is closed with X or cancel
}
});
}