[aquiaolado]

I know what you are saying. I did that. I read all the instructions. I join {#file}/{path}. It returns what I want but puts spaces between the expressions. But beside that I still need {#file}/{path}/{something that would return the filename from Calibre}.
Can we speak directly?

The Zotero works fine with the file you plugin/Calibre produces and with a file that was never inside zotero.

If I produce the RIS file with your plugin and then alter it manually to a file that zotero does not know it works.