@SampleScience no, directly in the Operating system, without virtual box.
So you keep the old version, how do you know your plugins work on the newer versions of macOS?
I'm asking because the vast majority of support requests I get are from macOS users who have compatibility problems. There are never any problems with Windows versions of my plugins, but for the moment I use Maize Sampler.
With Maize Sampler you have to align the version of macOS with a specific version of Maize (use the version of Maize that was out at the same time as the version of macOS), otherwise, you get problems.
I'm trying to switch to Hise but I'm having a different set of problems with it (mostly export and project management issues).