Branch:
https://github.com/RSuter/NSwag/tree/studio-uses-command-line
In the current version in the branch, you can select a runtime and the selected binary is used (this currently works only for "Generate Files"):

The build can be tested here:
https://ci.appveyor.com/project/rsuter/nswag-25x6o/build/2657
With the latest commit, the outputs are redirected to temp files so that "Generate" and display output in UI only also works.
I think all changes in NSwagStudio are now done (maybe more refactorings will come), can you please test with the latest CI artifacts:
https://ci.appveyor.com/project/rsuter/nswag-25x6o/build/2662
Yeap, it worked, thank you so much!
The only problem was that as my assemblies are .net core 2.0 and the default runtime is winx64, I got an error when loading my old powerhub.nswag file. Changing the runtime makes the error disappear, so maybe a friendly message saying that would be nice to the final user :)
Once again, thank you and congrats for such a great tool NSwagStudio is.

I changed the Runtime names from Core20 to NetCore20 => I think you got the error from this. Correct? Because you created the file with a prerelease build, this should not be a problem for the normal user...
Hmm.. it makes sense. Perfect :)
Isnt this error you posted as screenshot an issue?
Sorry, the error message cannot be easily avoided - we have to detect what type of assembly is selected and check the runtime with this... this will be a feature for the future :)
Added runtime detection for command line:

I think I'm done here :-), now we have to test this with as many projects as possible
We will test this with our solution after our first release.
Most helpful comment
In the current version in the branch, you can select a runtime and the selected binary is used (this currently works only for "Generate Files"):
The build can be tested here:
https://ci.appveyor.com/project/rsuter/nswag-25x6o/build/2657