> any way to back-convert a story into Twine 1?
If the Twine 2.x project is SugarCube based then you can do the following:
1. Convert your project into a TWEE file.
This can be done by using either: one of the third-party story formats like Entweedle or Illume; or by using the TweeGo utility's decompile option.
2. Create a new Twine 1.x project from the TWEE file.
This is done using the 1.x application's File > Import > Twee Source Code menu items.
Twine 1.x doesn't come with SugarCube so you will need to download it from the SugarCube 2.x website and install it.
The (vanilla) story formats that come with Twine 1.x are no longer fully compatible with modern web-browsers and should not be used to create a new project.