The Edit menu

Select Tree
add all trees based on all currently selected helices
Select drawing
select the current drawing
Deselect
deselect the current selection
Adjust selection
pops up the adjust selection dialog, which allows temporarily changing the selection based on search criteria.

Delete
Delete the selection. If a base is selected, the entire structure will be deleted (after confirmation is given.)
Cut
make a copy of the selected objects, and delete the original objects. Structure drawings are parts of them cannot be cut.
Copy
make a copy of the selected objects. Copies will always be labels, and initially unconnected to any structure, even if it are copies of structure objects (bases, etc.)
Paste
paste the objects in the clipboard to the current drawing.
Copy selection to clipboard (Windows)
produce an enhanced metafile in the clipboard of the selection
Copy drawing to clipboard (Windows)
produce an enhanced metafile in the clipboard of the current drawing
Copy page to clipboard (Windows)
produce an enhanced metafile in the clipboard of the entire page

Undo on
Turn undo feature on or off.
Undo
Oops, you made an error:you can undo your actions using this option: return your drawing to the state before your last action, or before that, or ...
Redo
Oops, you can use this if you have undone too much.
Undo steps
Sets the number of steps that can be undone
Clear undo
Clears the undo buffer