In the preferences/editor tab, the tab mode and behaviour can be configured with two comboboxes. The change of state seems to be saved correctly, however, GUI of the combobox always show the same string, i.e., "Insert Tabs" for tab mode and "Disabled" for behaviour. The combobox for color scheme in preferences/view seems to work fine. I found it Raspbian on Raspberry Pi 4.
This was fixed in version 0.4.2 (Bug 15075).