Thank you for your elaborate answer, however my problem remains.
tabSetting seems to influnce the width of a tabulator. It does not switch between spaces and tabs as relevant for the syntax of the language, just the appearance. So that doesn’t help.
I have no idea where that bespin.xml is saved, so I can’t manipulate it. Certainly not in the np++ folder or in MyDocuments. The bespin theme is also not metioned in any of the other xml files, no leads given…
Edit: I have found Bespin.xml on npp github, but the location I need to put it into doesn’t exist on my machine…
I think what I want is just out of scope for np++. Great editor nonetheless.