The command you give to scaffold a context when using a connection string from user secrets didn't work for me. I had to include the "ConnectionStrings." prefix, e.g.:
dotnet ef dbcontext scaffold Name=ConnectionStrings.Chinook Microsoft.EntityFrameworkCore.SqlServer

Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: e1601c3e-3f29-5d84-6350-2b38eeaf6adc
• Version Independent ID: 92a856d6-c5da-e215-46ac-d67c411f3ff9
• Content: Reverse Engineering - EF Core
• Content Source: entity-framework/core/managing-schemas/scaffolding.md
• Product: entity-framework
• Technology: entity-framework-core
• GitHub Login: @bricelam
• Microsoft Alias: bricelam