Thank you. However, with regard to your category of "docs" I've noticed that Alfred shows not only .png but also .jpg files because I opened a lot of them yestarday, which fulfilled almost whole of Recent-files workflow's list of recent docs. Therefore I was wondering if it won't be difficult to turn a custom category, say c2, into documents exclusively, i.e. excluding images altogether?
I've made some quick research and found a pretty handy web page with UTI types which may turn out to be useful for someone (see below). Nevertheless personally, I've finally come to a conclusion that unlike images there is far too many UTI file types for documents to be found out only there, let alone including .odt, .ods, and many other Open Office and Windows Office newest types (i.e. .xlsx, .docx, etc.), which are not listed on the page:
https://developer.apple.com/library/mac/documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html#//apple_ref/doc/uid/TP40009259-SW1
but hopefully, you know some simple solution to this document-only issue... And if there is no better solution than ferreting out a few-yard long list of UTI document types , I rather stick to the "doc" category of yours and my newly created custom category of "images".