I have a Solution with an Arduino project and a c# VisualStudio project for my local machine. 

I can compile both projects, the Arduino project building can be seen in the Micro Build Output.
However uploading using the menu Project / "Upload Last Arduino Build" does not work unless I switch the Startup Project to the Arduino Project.

Is there a way to avoid switching the Startup Project all the time ? 
Or: How would you easiest start the new Windows exe while having the Arduino project as the "main", from within VS ? ( I admit, that might be a non VisualMicro question )

If it's not that easy to remember which Arduino project was compiled last, the currently selected one ( which "Build only" refers to), is a good choice, agreed. 

I tried the right mouse context first (in vain), so if you add this enhancement fast, I still might get used to it.   

Again, thanks Tim, for your fast response.

I promised to invent a harder question next time, an accepted enhancement request is not that bad
But:
How do others deal with such scenarios? I think having an Arduino and a Windows project related to each other is a common  situation, especially when using VisualStudio ...
Sure, one gets used to switching the "active" project after a while (and true love does not complain)