Currently , it is mandatory to sign in to the web tool prior to being able to use it. It is also mandatory to be online in order to export any sort of APK, even a preview one to test on a device.
It would be less tedious for developers if the web tool could remember a device used to sign in, and sign-in wasn’t required constantly. This would allow developers to continue theme development even in the event of internet outages.
It would also be beneficial if Export Preview APK functionality worked regardless of internet connection status. The current implementation used to test themes is much less efficient than the PC version. Not only do you need to wait for themes to export, but it can take quite some time for an STP to upload to the server before the export even begins. This impedes developers who are working to identify bugs or test their themes on devices prior to final export.