I'd like it if there was a option is the widget section to add the notebook and note, as it seems as if thre is no widget for it.
Having all the widgets on the android widget section as well as in app will make it easier for us to see that there are actually more widgets available.
I think the 'Add to homescreen' button is tucked away and I thought it was for adding to an in app homescreen.
In conclusion, the 'add to homescreen' button is unclear in purpose (so maybe rephrase to 'add to phone homescreen' or 'make into widget), and its function should be added to the android widget section.