Visual Studio project configuration & environment

Thing I'm not getting here is very general, how do the configurations in Visual Studio projects work?

For each project there exists this launchSettings.json file which contains different logs/configurations. Each of these has its own Profile, Launch environment variables and other items.

1) Production

During app development it was necessary to create a different connection string since the production version of the app was being deployed to Azure.

I created corresponding connection string in appsettings.Production.json and my colleague helped me and set up the environmental variable ASPNETCORE_ENVIRONMENT = Production for me.

This is the configuration from launchSettings.json it created:

"SebastiansCookbook": {
      "commandName": "Project",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Production"
      },
      "dotnetRunMessages": "true",
      "applicationUrl": "https://localhost:5001;http://localhost:5000"
    },

Why is the Profile equal to "SebastiansCookbook" and not "ISS Express" or "Docker"? - SebastiansCookbook is name the solution, does this relate to more projects (whole solution) being built at once?

Why is the Launch equal to "Project" and not one of {"ISS", "ISS Express", "Snapshot Debugger", "Docker", "Executable"} - in fact, what are those anyways?

2) Testing environment

When creating tests for the application (in separate project referencing the WebApi project)

I had a problem that I believe originated from my lack of understanding of the topic of the first part of this post.

I had to create another connection string for the HttpClient I used for the tests. Following the practice of file per environment, I created appsettings.Testing.json file and put the connection string there.

The problem I encountered was "How to force the WebApplicationBuilder to use this appsettings file". And even tho the solution is relatively simple and already presented in the following thread: Set environment in integration tests I still have a question.

What I wanted to do before I was recommended this solution was to create new "configuration" for the WebApi project. I thought that if I specified the environmental variable ASPNETCORE_ENVIRONMENT = Testing I will have succeeded. There are couple of points before my question:

1. I haven't thought about how would I make the WebApi project to use this configuration from the Testing project...
2. I couldn't understand how would I even create the configuration - I thought as much as that if I were to create the configuration for the same Profile and Launch but with a different value to the environmental variable ASPNETCORE_ENVIRONMENT there would be a conflict

So my idea here was to use different Profile or at least Launch but since I didn't understand their meaning I couldn't. (Here actually came the question of forcing the project to use a configuration...)

Now to the question: Is it possible to set a project to use a configuration from another project? Is it also possible to somehow create another configuration like I wanted to do?