[CyberPaul]

Well, that would make kobopatch file totally unhelpful. If I still need to change one of the files, there is no value in using this mechanism.
However I tried the below format and I didn't get any error from the patching process. Are you sure it is not accepted?

src/libnickel.so.1.0.0.yaml:
    My 24 line spacing values: yes
    Custom font sizes: yes
    Set KePub hyphenation: yes
    Change Wikipedia search language: yes
      - FindReplaceString:
          Find:    "\0https://%1.m.wikipedia.org/wiki/Special:Search\0"
          Replace: "\0https://it.m.wikipedia.org/wiki/Special:Search\0"
      - FindReplaceString:
          Find:    "\0https://%1.wikipedia.org/wiki/Special:Search\0"
          Replace: "\0https://it.wikipedia.org/wiki/Special:Search\0"
    Always show confirmation dialog before upgrading: yes
    Unify font sizes: yes