I do look forward to a complete version of this exporter, as a Godot user exporting as png is the only option. I have used it successfully for my main player character in my latest project but it was rather painful having to export each animation separately.
The image sequence thing is not such a large issue since Godot has excellent animation support allowing me to import them all as AnimatedSprite2D. However convenience is always nice to have and a complete sprite sheet I believe is the ideal outcome.
Thank you for the great work on this, the tool in general is fantastic, and the exporting is just the icing on the beautiful cake.