Do not convert spaces to tabs in verbatim
In a verbatim block, zim automatically converts four spaces to a tab character.
In a verbatim block, nothing should be converted.
Also, in verbatim blocks, zim displays tabs as eight spaces, which is inconsistent with the four spaces above. I'm not sure how to change this. (I can see the config file allows specification by pixels, but not by fixed-width spaces.)
which refers to on-the-fly conversion from tab back to spaces, but IMO zim should never convert spaces to tabs in the first place.