For instance in Unity projects there's two csproj files:
Assembly-CSharp-Editor.csproj and Assembly-CSharp.csproj
While some of the files should be added toAssembly-CSharp.csproj, others should be added to Assembly-CSharp-Editor.csproj.
Prompting to add file to one csproj, while ignoring another would be nice.
Supplying multiple options in the file drop-down menu would also be nice.