The closest I've got is displaying a MRVS, but unfortunately adding a new entry is not possible. Fixing this isn't possible in an OOTB way and as such I suggest you to instead give method a try:
0.) Read this post: https://www.servicenow.com/community/developer-articles/show-case-the-service-portal-experience-app-...
1.) Create two custom tables (one for the main form and one for the "MRVS" table) with proper ACLs
2.) Configure the Form of the custom table to your likings
3.) Add a new (custom!) relationship that will allow you to put the MRVS table on the main form as an "embedded list"
If you're interested in the "public MRVS display way":
1.) Create a new public page
2.) Create a new Scoped Cache named "public_cat_items"
3.) Add a new Widget Instance with the following widget:
HTML:
<sp-widget widget="::data.cat_item" />
Server Script:
(function() {
data.cat_item = $sp.getWidget("widget-sc-cat-item-v2");
var itemSysID = $sp.getParameter("sys_id") + "";
var guestCriterias = ["76f09af6cb1200108ad442fcf7076dbf"];
var cGr = new GlideRecord('sc_cat_item_user_criteria_mtom');
cGr.addQuery("sc_cat_item", itemSysID);
cGr.addQuery("user_criteria", "IN", guestCriterias);
cGr.setLimit(1);
cGr.query();
if (cGr.hasNext()) {
var catItem = null;
if (gs.getUser().getName() == "guest") {
catItem = JSON.parse(sn_scoped_cache.ScopedCacheManager.get('public_cat_items', itemSysID));
} else {
catItem = $sp.getCatalogItem({
sys_id: itemSysID,
is_ordering: true
});
sn_scoped_cache.ScopedCacheManager.put('public_cat_items', itemSysID, JSON.stringify(catItem));
}
if (catItem) {
data.cat_item.data.sc_cat_item = catItem;
}
}
})();
4.) You need to load the public page using an regular/admin user first (this makes the widget load the full catalog item variables + mrvs).
5.) Loading the widget as a "Guest" user will then show the catalog item (but again: the MRVS "Add Row" Popup will show an empty dialog....)
