Deleted notes are listed in the "Deleted Notes" dialog (Global Menu → Show Deleted Notes) and can be restored by pressing the "undelete" link.

If a note has child notes, they will be restored along with it. Should the original location no longer exist (e.g. the parent has been deleted), the note will be restored into the default location for new notes (Note Inbox).

When a note is hoisted in the tree, the dialog will only display notes deleted from the subtree of that hoisted note.

To permanently erase deleted notes and clear the list, press the three-dots menu and select "Erase deleted notes now".

Deleted notes are permanently erased after a certain amount of time (7 days by default). To change this interval, press the three-dots menu and select "Deleted Notes Settings".