Use another list to keep your numbers and then pull in the last number in the form...Do a calculation to +1
Set that as your ID and also update the other List on Save....That should work as long as users have contribute to both list.
Hi @smithme
I had a similar requirement and implemented this using the spSaved event. The code below executes after the item was saved, retrieves the SharePoint item ID and I update the Title field with a unique reference.
fd.spSaved(function(result){
//Get the current list ID
var listId = fd.spFormCtx.ListAttributes.Id;
//Get the saved item ID
var itemId = result.Id;
//Get a value from one of the drop down fields
var site = fd.field('Site').value.Cost_x0020_Centre;
//Compose a unique reference
var title = "FC-" + site + "-" + itemId;
//Get the SharePoint list
var list = pnp.sp.web.lists.getById(listId);
//Update the saved item
list.items.getById(itemId).update({
Title: title,
Status: "Open"
}).then(function() {
console.log('New Item Id', itemId);
});
});