I've been using CoRD heavily over the last few years, in my day-to-day job where I need to connect to Microsoft RDP servers. CoRD is perfect for my needs, mainly as it presents a single "unified" view: rather than having lots of windows open, there's just one window for all connected servers, and I click between which one I want to view.
However, CoRD was a bit flaky on Yosemite, and is downright unstable on El Capitan. I've tried various other RDP packages, including the "official" Microsoft client, but none of them are as simple and/or useful as CoRD.
CoRD development seems to have been abandoned years ago. Does anyone know of an alternative RDP client that'll easily support multiple simultaneous connections, preferably in a single window?