There is none. You should make a request for documentation on the git hub repo site:
If you have a specific question please post it.
Personally I just want to know how the thing works. A simple document that explains this would be great. Only functionality I am interest in at this time is how to copy other user story map or app templates.
AGO Assistant uses the ArcGIS REST API to help users work with their ArcGIS Online and Portal for ArcGIS content. Since Esri Support Services does not directly support this tool, users can direct their concerns and ideas for improvement on this GitHub page.
The following workflow can be used to move hosted content from one AGOL organizational account to another:
*Please note that this only works for feature layers and web maps, you cannot move storymaps and apps.*
There are additional resources on the About Page on the https://ago-assistant.esri.com/ website.
Could you please the confirm the part around 'users can direct their concerns and ideas for improvement on this GitHub page' as I have seen comments in the issues log that it's no longer supported in it's current form?