All changes in structure (adding / deleting Main Nodes, adding or/and editing Comments) are saved to file automatically. That is why only Save As menu item is present in ART. To save structure to other file, choose File/Save As in the menu or click the Save As button.
Saving time is displayed on the status bar.
ART allows saving up to 100 Registry copies (Main Nodes) in the same file.
You may delete any copy (Main Node) as well. To do this highlight the Main Node to be deleted, choose Delete in the context menu and confirm deleting.