I have 1 app that I use that isn’t compatible with High Sierra preventing me from upgrading. I have a Samsung T5 external SSD which I have partitioned to run Windows 10 boot camp. Can I create another partition on that external SSD and install Sierra on it for when I need to use that one app then install High Sierra on my internal SSD? Kinda like having a triple boot system covering all my bases until that app is compatible.