I wonder why there are three different editor tabs in the collection entry type. Is there a reason for it? Maybe my creativity is not such to envisage a use for three different editor tab, since the editors can be coded as Doe, J. and Knopp, O. and Dietz, T. I feel confused.
Regards
Bernhard
It’s there, because it’s in the biblatex spec 
It allows you to define multiple editors with different roles. E.g. you have one main editor and then you maybe have a secondardy editor whose job is redactor or reviser. It also allows complicated things as Founder (The founding editor of a periodical or a comprehensive publication project such as a
‘Collected Works’ edition or a long-running legal commentary)
See §2.6.3 of the biblatex manual for an explanation of the roles and combinations.
ftp://ftp.tu-chemnitz.de/pub/tex/macros/latex/contrib/biblatex/doc/biblatex.pdf
I must admit, it’s the first time I stumbled across this…