Für ein möglichst sauberes Ergebnis würde ich
\documentclass[ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[backend=biber, style=alphabetic]{biblatex}
\DeclareSourcemap{
\maps[datatype=bibtex, overwrite]{
\map{
\step[starnocited=true, final]
\step[fieldset=keywords, fieldvalue={, }, appendstrict]
\step[fieldset=keywords, fieldvalue=nocited, append]
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\step[fieldset=options, fieldvalue=skiplab, append]
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\defbibenvironment{nolabbib}
{\list
{}
{\setlength{\leftmargin}{\bibhang}%
\setlength{\itemindent}{-\leftmargin}%
\setlength{\itemsep}{\bibitemsep}%
\setlength{\parsep}{\bibparsep}}}
{\endlist}
{\item}
\begin{filecontents}{\jobname.bib}
@article{sigfridsson,
author = {Sigfridsson, Emma and Ryde, Ulf},
title = {Comparison of methods for deriving atomic charges from the
electrostatic potential and moments},
journaltitle = {Journal of Computational Chemistry},
date = 1998,
volume = 19,
number = 4,
pages = {377-395},
doi = {10.1002/(SICI)1096-987X(199803)19:4<377::AID-JCC1>3.0.CO;2-P},
}
@book{worman,
author = {Worman, Nancy},
title = {The Cast of Character},
date = 2002,
publisher = {University of Texas Press},
location = {Austin},
}
@thesis{geer,
author = {de Geer, Ingrid},
title = {Earl, Saint, Bishop, Skald~-- and Music},
type = {phdthesis},
institution = {Uppsala Universitet},
date = 1985,
subtitle = {The {Orkney Earldom} of the Twelfth Century. {A} Musicological
Study},
location = {Uppsala},
}
@book{nussbaum,
author = {Nussbaum, Martha},
title = {Aristotle's \mkbibquote{De Motu Animalium}},
date = 1978,
publisher = {Princeton University Press},
location = {Princeton},
keywords = {secondary},
}
@incollection{pines,
author = {Pines, Shlomo},
editor = {Twersky, Isadore},
title = {The Limitations of Human Knowledge According to {Al-Farabi}, {ibn
Bajja}, and {Maimonides}},
date = 1979,
booktitle = {Studies in Medieval {Jewish} History and Literature},
publisher = {Harvard University Press},
location = {Cambridge, Mass.},
pages = {82-109},
keywords = {secondary},
}
@book{knuth:ct:b,
author = {Knuth, Donald E.},
title = {{\TeX}: The Program},
date = 1986,
maintitle = {Computers \& Typesetting},
volume = {B},
publisher = {Addison-Wesley},
location = {Reading, Mass.},
sorttitle = {Computers & Typesetting B},
}
@book{knuth:ct:c,
author = {Knuth, Donald E.},
title = {The {METAFONTbook}},
date = 1986,
maintitle = {Computers \& Typesetting},
volume = {C},
publisher = {Addison-Wesley},
location = {Reading, Mass.},
sorttitle = {Computers & Typesetting C},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
Lorem \autocite{sigfridsson,worman,nussbaum,knuth:ct:b}
\nocite{*}
\printbibliography[
notkeyword=nocited,
heading=bibintoc,
title={Literaturverzeichnis},
]
\printbibliography[
env=nolabbib,
keyword=nocited,
heading=bibintoc,
title={Weiterführende, Ergänzende Literatur},
]
\end{document}
vorschlagen.
Statt mit
categorys wie in
https://tex.stackexchange.com/q/6967/35864 arbeiten wir hier mit dem
sourcemap-Feature, das ein
keyword setzt. Das hat den Vorteil, dass wir
biblatex sagen können, dass wir für die Quellen, die nur wegen
\nocite{*} da sind, kein Label benötigen. Das verhindert im Beispiel, dass
knuth:ct:b als Label unnötigerweise "Knu86a" wird.
Der Trick ist es dann, für die weiterführende Literatur eine andere
bibenvironment zu definieren, die das Label, das eh leer wäre, ganz weglässt.