Removed "Spherical" checkbox, since there's no point in using the app if your video isn't spherical.
Added a message at the top indicating you need to click Open to get started. (Ideally we'd probably replace the single dialog with a wizard flow, but this change is quicker.)
Expanded other checkbox labels to be less "restaurant menu" and more "statements of truth".
Removed projection info string, as it's not user-actionable and implies some kind of projection type inference that is not actually happening.
Removed spatial audio info string from UI to reduce UI noise. Detected spatial audio format is now written to the console in case anyone really needs it.
Renamed "Save as" button to "Inject metadata" for a stronger call to action.
Removed "Quit" button to reduce chance of quitting without injecting metadata.
Quick tweaks to layout and alignment.
Made green message text blue (green was hard to read on the white background).