Hello @wasim13​ 

You should use the kml_data{}.name and kml_data{}.value list structure to write extended data with the KML writer (documented here). You should be able to use an AttributeExploder (explode as list) to create this list structure. You will have to use the Ignore Attributes Containing parameter to exclude any attributes you do not want written as extended data.

I have attached an example demonstrating this workflow and I hope it helps!