Any letter
Go to editing item name
Double click
+
Add new item (above the current)
Ctrl+Down
Add new item (below the current)
Right
Move an item in submenu
Left
Move an item one level up
Delete
Delete item
Ctrl+B / Ctrl+I / Ctrl+U
Change font style: boldn, italic, underline
Shift+Up/Down
Select a group of items
Shift+Click
Ctrl+Click
Ctrl+A
Select all