I want to be able to say to only use a particular repository for one package, and stick to nuget.org for the others.

Example:

I've got https://dotnet.myget.org/F/dotnet-core/api/v3/index.json enabled so I can use Microsoft.Packaging.Tools.Trimming.

Unfortunately this means a whole lot of other pre-alpha packages show up as the "latest" versions available because there's no way to set priorities or preferences for package sources

maintainer edit

Design available at #10660