Pb editing a reference

(X3, Mac)

Hi, I have been using Endnote for a while but it’s the first time I am enable to edit a reference.

I collect these refrences from EBSCO, through Zotero. After that, I export from Zotero in various format (RIS, Refer) and import in my library as usual. But this time it’s impossible to edit the reference in order to change one of the custom field I use.

Does anybody, have already this kind of difficulty ? and hopefully a solution.