Hello Sweta,
First thing to do is to update the Interaction Scripting Editor.
To do that please follow the instructions and implement note
https://service.sap.com/sap/support/notes/1699205
Are you directly draging the button to dialog part. You should double click dialog part and drag the
button to button area instead.
https://service.sap.com/sap/support/notes/1376127
Regards,
Reshma Rao