From FreeCAD Documentation
- Select the File → Close All option from the menu.
- If there are unsaved documents a dialog box will prompt you to save them:
- Press the Save button to save the active document. If required enter a filename first.
- Press the Discard button to discard the active document and lose all changes.
- Press the Cancel button to cancel the command.
- If there are multiple unsaved documents you can check the Apply answer to all checkbox to avoid being prompted for each unsaved document separately.