JSON Text Document - SmartJSONEditor/PublicDocuments GitHub Wiki
JSON Text Documents (.json) file extension files are very basic JSON text formatted files that by its definition do not support saving of extended features that Smart JSON Editor offers.
Smart JSON Editor cannot store extended editing features in .json files as per definition of .json file basic text format
When Opening .json files:
https://github.com/SmartJSONEditor/PublicDocuments/blob/master/Images/JsonFileEditingDisabled.png
- New Project Node menu is disabled (Folder, Model, Note) nodes addition are disabled. JSON Text file do not allow multiple root objects
- Only single Project Node is created with file name.
You are not allowed to use API Groups, Folders or any Project nodes as JSON Text file specification do not allow it.
When Saving .json files:

- Document will be exported as JSON Text file taking in account "Human Readable" settings (not formatted or visually formatted JSON text)
- Disabled Json Nodes are not exported (Take in your advantage)
- Value Transformer values are exported
During editing .json file, you can use Smart Objects, Value Transformers etc, however upon closing the document all extra information is lost as textual json file do not allow any of extended features being saved. Only JSON text is stored in .json file.
Always preffer using .sjson Project Document files and import JSON Text Files instead of opening them directly.