Folders in Document Tabular Section or ValueTree

Hallo,
i create a document called "Invoice" with Tabular Section called "items".
Now i want to show the items in a hierarchical list eg.
root
|_  Item 1
    item 2
    <Folder>
    |_ Item 1
        Item 2
    Item3

how can I create a folder in the tabular section? Can anybody help?

i forgot, i work with managed forms.

Hi, mkolhoff, for that you can use ValueTree form attribute and load/save data into/from it on read/write your document.

Hallo Samuel,

thanks, that is what i also tested but i can only insert a new row, not a new folder.

You can change row picture for it to folder and make it look like a folder. Use custom command for this kind of rows creation.