thanks for your aproach. Have you managed to work out a better solution?

I have the follwing code for ‘humanities’ / MLA style and I am not able to get it work.
Ok the first lines need to be taken out since LYX has its own options. But how do I integrate all the redefinitions? I always receive some error code :(

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\documentclass[12pt, oneside, a4paper, BCOR14.5mm, DIV12, headsepline, normalheadings, draft]{scrreprt}
\usepackage{mathptmx}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{graphicx,textcomp,booktabs,amsmath}
\usepackage{setspace}\doublespacing
%\onehalfspacing %

% from here on I believe it shold only be prompted to LYX preamble settings…

\usepackage[UKenglish]{babel}
\usepackage{mla6}

\jurabibsetup{
authorformat={citationreversed,reducedifibidem,firstnotreversed},
citefull=first,
round,% — JMC
endnote=false,% — JMC
annotatorfirstsep=qtd,% — JMC
% idem=strict,% — JMC %—->the MLA Handbook says those options should be avoided, if, however, you want to use them, delete the %
% ibidem=strict,% — JMC %—->the MLA Handbook says those options should be avoided, if, however, you want to use them, delete the %
% pages=ignoreibidem,% — JMC (new option in latest beta) crossref=long %—->the MLA Handbook says those options should be avoided, if, however, you want to use them, delete the %
crossref=long,
titleformat=commasep,
bibformat=ibidem,
}

\AddTo\bibsenglish{%
\def\edbyname{}
\def\Edbyname{ed.}
\def\inname{\unskip}
\def\editorname{\unskip,\space ed.}
\def\editorsname{\unskip,\space eds.}
\def\etalname{et al\periodn}
\renewcommand*{\trans}{trans.}
\renewcommand*{\ibidemname}{}
\renewcommand*{\ibidemmidname}{}
\renewcommand*{\idemname}{}
\renewcommand*{\idemmidname}{}
\renewcommand*{\firstedname}{1\textsuperscript{st}}
\renewcommand*{\secondedname}{2\textsuperscript{nd}}
\renewcommand*{\thirdedname}{3\textsuperscript{rd}}
\renewcommand*{\fourthedname}{4\textsuperscript{th}}
\renewcommand*{\fifthedname}{5\textsuprescript{th}}
\renewcommand*{\thedname}{\textsuperscript{th}}
\renewcommand*{\editionname}{ed.}
\renewcommand*{\urldatecomment}{\unskip\commas}
\biburlfont{rm}
}
\addto\jbonlyforbib{%
\DeclareRobustCommand{\mla}{. }
\DeclareRobustCommand{\mlaws}{.}
\DeclareRobustCommand{\commas}{ }
\DeclareRobustCommand{\periodn}{}
\DeclareRobustCommand{\nosnoc}{.}
\DeclareRobustCommand{\commanot}{}
\DeclareRobustCommand{\nocolon}{:}
\DeclareRobustCommand{\diss}{Diss}
\DeclareRobustCommand{\perf}{Perf.}
\DeclareRobustCommand{\dir}{Dir.}
\DeclareRobustCommand{\reviewintro}{Rev. of }
\DeclareRobustCommand{\specintro}{Spec. issue of }
\DeclareRobustCommand{\Edbyname}{Ed.}
\DeclareRobustCommand{\editorname}{\unskip,\space ed}
\DeclareRobustCommand{\editorsname}{\unskip,\space eds}
\DeclareRobustCommand{\revedname}{Rev.}
\DeclareRobustCommand{\editionname}{ed}
\DeclareRobustCommand{\trans}{Trans.}
\DeclareRobustCommand{\bibapyldelim}{}
\DeclareRobustCommand{\bibapyrdelim}{}
\renewcommand*{\bibtfont}{\textit}
\renewcommand*{\bibbtfont}{\textit}
\renewcommand*{\bibjtfont}{\textit}
\renewcommand{\bibauthormultiple}{—. }
}