Following this question BibLaTeX/BibTeX custom field to show file link and Notes after bibliography entry with Biber and biblatex I get it to work (well, more or less). In the code below I defined a field file and mynote. It is working for file but not for mynote. I don't understand why!
\documentclass[%
a4paper,
english,
11pt,
]{article}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{Padial:2010,
title={The integrative future of taxonomy},
author={José M.~Padial and Aurélien Miralles and Ignacio De la Riva and Miguel Vences},
journal={Frontiers in Zoology},
year=2010,
month=may,
volume=7,
number=16,
pages={1--14},
doi={10.1186/1742-9994-7-16},
issn={1742-9994},
mynote={Very good book!},
file={./article/2010_Wang.pdf},
keywords={biology, taxonomy},
}
\end{filecontents*}
\usepackage{fixltx2e}
\usepackage{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{type1ec}
%\usepackage{lmodern}
\usepackage{microtype}
\usepackage[%
left=5cm,
right=2cm,
%showframe,
]{geometry}
\usepackage[color,notref,notcite]{showkeys}
\usepackage[strict,autostyle]{csquotes}
\usepackage[%
backend=biber,
style=ieee,
]{biblatex}
\DeclareRangeChars{~,;-+/{}} % add '{}' as page range delimiter
\addbibresource{\jobname.bib}
\DeclareFieldFormat{mynote}{\textbf{#1}}
\DeclareFieldFormat{file}{\href{file:#1}{\textbf{Open file}}}
\AtEveryBibitem{%
\csappto{blx@bbx@\thefield{entrytype}}{% put at end of entry
\iffieldundef{file}{\space \textbf{No file!}}{%
\space \printfield{file}}
\iffieldundef{mynote}{\space \textbf{No annotation!}}{\space\printfield{mynote}}
}
}
\usepackage[%
colorlinks,
unicode,
breaklinks,
]{hyperref}
\begin{document}
\nocite{*} % list all entries
\printbibliography
%\printbibliography[keyword=taxonomy]
\end{document}

annotation(as it is already defined in BibLaTeX) and did as I had done forfile. – cacamailg May 02 '13 at 14:53mynoteseems to fall into the purpose ofannotation). I must say that IMHO, while this answer works fine and is a good approach to single files, Guido's answer seems to me to be the "right" one to choose, since it approaches the subject in a more generalized way. – henrique May 02 '13 at 19:46user[a-f]etc.). There were a typo in Guido's answer (filedinstead offield). Perhaps if you try now? I just ran it with my MWE, only changing where I useduserato the newmynotefield with no apparent problem. I insist that his is the correct answer because it addresses more general usage and makes use of the full power of biblatex+biber. – henrique Nov 25 '14 at 19:13