I think that there is a chance again this year of having FLL release a scoring tool, but I don't know what the timeframe would be. That's based on the recent development of new tournament scoring software.
When a team comes to me and thinks that their scoresheet was scored incorrectly because a scoring app tells them something different, here's what I do.
I grab a pen or pencil, the scoresheet, and the mission descriptions, and I go through the scoresheet questions, writing the mission scores down along the way. Then I add them up.
Teams that validate their scoring apps by hand from time to time based on the missions that they are doing, can feel confident that what they have is good enough for development purposes.