Answer: Use name connectionStrings in app.config for Scaffold-DbContext EF 6 command

In my case (VS2022, .NET 6) I also encountered the same problem n got solution in following way;

1. Added Connection String in appsettings.json file (Screenshot attached)
2. Ran the command: PM> Scaffold-DbContext name=StudentDbConnectionString TrustServerCertificate=true;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models
3. It generated relevant DbContext file (Screenshot attached)
4. Manually registered DbContext in Builder.Services in program.cs…