Not being a mac user myself and having a handful of potential Windows clients, I prioritised the Windows version. But electron makes it very easy to build a macOS version too, so this was ready earlier than I expected.
Since the app is video-related and most professional video editors still use macOS, this is an important step. The free app is great for casual users, but the premium one is much more convenient for professionals that need to batch-process lots of GoPro video files.
Next steps: marketing materials, Linux command-line version, After Effects templates.