To customize a note's editor:
Right click on the titlebar of the note.
Select Note preferences...
The Local Settings - Knotes dialog will open.
Choose the Editor icon from the three icons at the left.
The following choices are available:
This is the size of the tab in spaces. Edit this number as desired.
This is a checkbox. If selected, auto-indenting is on.
Click this button to open the standard KDE font selection dialog.