Entity Developer supports File > New > Project > ASP.NET Core Web Application (.NET Framework): just right click project in Solution Explorer > Add > New Item > Devart EF Core Model (*.efml).
Entity Developer doesn't support File > New > Project > ASP.NET Core Web Application (.NET Core) because .NET Core projects do not support the "Custom Tool" property of project items, so we cannot integrate Entity Developer into .NET Core projects at the moment:
https://github.com/daveaglick/Scripty/issues/49. As a workaround, you can use a standalone Entity Developer to manage your model and generate the code.