After making changes in the Assembly Kit, which you either want to back up for personal use, to make a future update easier, or to share Assembly Kit data with someone else:
Navigate to your assembly kit folder, within Steam/steamapps/common/%name of the game%/assembly_kit Navigate to assembly_kit/raw_data/db, and find “update_commands.txt” Open the file, remove the top line which says “Update by xyz …”, save the file, and move the file to somewhere secure elsewhere on your memory. Don’t rename the file. And now you have a backup which you can refer to at any point.
To load data up from a update_commands.txt, grab a completely fresh install of the AssKit. Within the session, use Extra Tasks -> Apply Commands from File Navigate to the update_commands.txt, and the program will add in all your data!