Comment by anonymars

Huh? The registry thing is for a specific niche*, not just "multiple processes"

You just set the startup properties on the solution to start the multiple projects. On that page, look for "To set the startup project or multiple projects from solution Properties" (https://learn.microsoft.com/en-us/visualstudio/debugger/debu...)

* "Sometimes, you might need to debug the startup code for an app that is launched by another process. Examples include services and custom setup actions"

Starting multiple copies of the IDE wouldn't handle these scenarios either