Hi, we are a team of UX designers that works with MacBooks and while Indigo.Design Desktop can be run on a pre-Catalina macOS or in a VM, it's really not a viable option right now, because:
This takes me to the question of IF (i hope so, given Silverlight being EOLed even on Windows) you plan to release a new version that would use different technology. And more importantly – WHEN?
I agree that using a VM or holding back your mac versions are not viable options. Unfortunately, we won't be able to update the desktop app to run on Catalina due to deep platform changes introduced by OS X w.r.t. 32-bit apps. It's out our control, and feel helpless in that regard. It was never our intention to disrupt your work.
To answer your other question-- yes, we are working on a different design tool, This will run directly in your browser and will allow you to create designs from scratch using a consistent design language (using real UI components). With this new effort, we are aiming to provide a high degree of reuse when it you are ready to implement your designs. This tool is focused on higher fidelity designs and code generation, and not state-based prototyping features currently available in the desktop app. We are hoping to preview this tool very soon to get early feedback and match your usage scenarios.
If possible, can you share some examples of designs you are creating for your development team? I can take a look and tell you whether our new tool will fit your needs. You can email us at email@example.com to share privately.
Assuming you are using Sketch to create your designs, have you explored publishing it directly to the cloud using Indigo.Design plugin for Sketch? Or are you referring to exporting from Sketch and editing the flows in the desktop app?