You can create a new Notezilla sticky note from within an existing note. Just press Ctrl+N shortcut key to create a new note when you are inside another sticky note.
You can configure the left mouse click or double mouse click (on Notezilla icon) to create new note. To configure, go to Notezilla Preferences-->General Tab. To access Notezilla 's Preferences, right click on Notezilla icon and choose Preferences from the menu.
Also, you can use the hotkey Ctrl+Shift+U to create new note instantly. Hope this helps.
Adding a separate button/icon for this is in our to do list. Hopefully, will be added in future versions. Can't promise though :)