Is there any property defined for mentioning Slug area inside PrinceXML.

The bleed and trim area can be adjusted with this CSS:

@page {
    marks: crop cross;
    prince-bleed: 5mm;
    prince-trim: 10mm
}

You can create slug lines using page margin boxes with tricks like negative margins.

@page:right {
        @bottom-right {
            content: 'string(section-title-str);
            vertical-align: bottom;
            margin-bottom: -20pt;
        }
}