Is there a way modify the size and shape of the notes window?
If you mean the notes popup that appears when you tap the notes icon, no.
If you mean the notes field that appears on some layouts, yes, you can edit the layout and resize the field:
http://www.arlomedia.com/apps/setlistmaker/tutorials/changing_layouts.html
If that doesn't answer your question, please post a screen shot showing what you want to resize.