How can we stop this dialogue box when we click on save option?

sireesha said:

please explain little mor on this

Which part?  There were a few different things there.

What do you mean? No, you can't! There is unsaved data in the form. And Appian does not know that you somehow persisted it in the background.

But, to get rid of this, why not just hide the input fields and show a success message to the user. Then he/she can easily navigate away. This would also make this a less awkward user experience.

This part

sireesha said:

But, to get rid of this, why not just hide the input fields and show a success message to the user.

After the user presses your "save" button, and after the "save process" is completed successfully, hide the editable portions of the interface.  When there are no editable fields with (what Appian thinks of as) "unsaved" data being displayed, the "unsaved data" warning dialog you're talking about here will not be displayed when the user attempts to navigate away.