Hi Sathya,
In HtmlSnippet widget, if you try to copy huge no.of lines of code, it will take longer time to paste. Even after pasting the html code, once you click on Save button, it will respond late. So in this case the best way to achieve this is by passing the file path in ExternalFile. At first you should paste your html file in the theme folder of your project directory.
Then pass the the file name in ExternalFile label of Html snippet.Refer below:
Hope it will be helpful!