In response to a tweet asking to save all groups, I responded that there is no API for Save Group. That’s true, but all hope is not lost.
This video shows how the API can be used to generate a text file listing all model groups. Then this text file is used as input to a journal file that saves each group to its own file.
Boost Your BIM 
Is there currently a more thorough explanation of what you are doing here? or would you be willing to share the Macro and SaveGroupsJournalFile.txt you use in this demonstration?
Hi,
Please contact me at https://boostyourbim.wordpress.com/contact/ to discuss this.
Regards
Harry
You have a group which includes a floor. Did this actually get converted over to a family? Was the floor created via a system family or was it simply an extrusion? I would love to know if a work around exists to include system families in custom families. 🙂
Hi – This API/Journal file routine does not involve families. The groups get saved to RVT files just as if you did File-Save As-Libary-Group in the Revit UI.
This post “How to create a family containing walls, doors etc ” might be of interest:
https://forums.autodesk.com/t5/revit-architecture-forum/how-to-create-a-family-containing-walls-doors-etc/td-p/6679155