stcinder

I couldn't easily find a reference in the Human Interface guidelines, although [CNET mentions it](https://www.cnet.com/tech/computing/how-to-open-multiple-instances-of-an-application-in-os-x/): On a Mac you never have multiple instances of an app. One instance runs all...

Tabs come for free with the MacOS, so if you can fix the multi-instance problem, it will fix the tabs at the same time.