While Generating Eway bill, A dialog box appears that Some fields are mandatory for GSTR-1

GSTR-1 fields are mandatory only if you want to auto fill data or Import EWB Data to file GSTR-1. You can ignore this, if you are not using that functionality otherwise you can face errors at that stage.

For details of what you are missing while generating E-way Bill. Please share the Eway bill creation screenshot.