I have recently change my simple xml to advance xml and I cannot find a way to change it back. I used ?showsource=true to see advance xml.
You cannot. Simple XML is essentially just a simplified interface to advanced XML that implements only a subset of everything you can do in advanced XML. What you see when you add ?showsource=1 at the end is the XML code that Splunk is really using - the simple XML is translated to advanced XML internally. This translation is one-way, so you cannot convert advanced XML to simple XML.
You cannot. Simple XML is essentially just a simplified interface to advanced XML that implements only a subset of everything you can do in advanced XML. What you see when you add ?showsource=1 at the end is the XML code that Splunk is really using - the simple XML is translated to advanced XML internally. This translation is one-way, so you cannot convert advanced XML to simple XML.