Not sure what you mean – do you mean a “Saving the form, please wait” dialog? – if so, you can use something like this in the dffs_PreSaveAction function in Custom JS:
var dlgId = spjs.modal.add({
"title":"Saving the form",
"html": "<div style='height:30px;'><img src='"+_spPageContextInfo.webServerRelativeUrl+"/_layouts/15/images/gears_anv4.gif' style='vertical-align:middle;margin-right:10px;'>Please wait...</div>",
"width": 250,
"showFooter": false,
"showClose": false,
"allowMaximize": false,
"resizable": false
});
setTimeout(function(){
spjs.modal.cancel(dlgId);
},10000);
This will auto close after 10 seconds in case there are some kind of error saving the form .
Alexander