Most common and easy use-case is to generate e-way bill at time of creating sales invoice. Hisab has already made it simple. However, sometimes, you may want to generate e-way bill at later stage.
For example, Sales invoice is created and later on you need to generate e-way bill.
When you perform above action, and if sales invoice had any missing details like HSN code, transportation id, pin code or so, it will open a dialog to first fill that details. Once you fill all asked details, you can create e-way bill.
If you are facing any issues with this, please refer to troubleshooting guide.