It seems to me that there's no such equivalent to spreadsheets for NoSQL / object databases (and even graph databases). There's nothing (to my knowledge) in common office suites for storing object type data (i.e. with a less defined schema) with a user-friendly interface. And this is a gap that should be filled.
Each document (file) would contain combinations of lists and objects similar to JSON. In the GUI, the user would be able to add objects and lists to the document, and remove them and delete them. And then with these elements the user would be able to add items to the list, and add properties to objects.
I would also envisage some kind of ability to do formulae like in spreadsheet programs. For example, the property of object B is calculated by reference to a property of object A. So the user would be able to specify unique identifiers for the object and then be able to look up objects and access their properties.
Such a program would be able to save data in XML and JSON for easy transfer to other applications.