View more than one project/solution in Visual Studio

There's a much easier (but not so obvious) way; right click on the Visual Studio icon in the taskbar, then right click on the application name in the popup menu, then click "Open". Windows will then open another instance where you can open another solution in.

This is the way Visual Studio is designed: One solution, one Visual Studio (VS) instance.

Besides switching between solutions in one VS instance, you can also open another VS instance and open your other solution with that one. Next to solutions there are as you said "projects". You can have multiple projects within one solution and therefore view many projects at the same time.