To customize the editor:
Right click on the panel icon.
Select Preferences...
The KNotes Defaults - 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.