There are several meta-taggers out there that are like what you’re asking. Google ‘file tagger’.
As nefycee notes, the alt-c quick-open is excellent for drilling down to find the file you want, and a double-click opens the file par normale. In my use of Tabbles the GUI is more of a help than hindrance to focus me on the info or docs I want to find and, for the casual users I know, it helps in creating a Tabbles database rather than simply meta-tagging a bunch of files. Gives them more of a ‘project space’ feeling.
Andrea: I think he’s talking more about accessing files outside of the Tabbles GUI. The explorer integrated right-click is (at the moment) geared toward adding a file to a Tabbles DB rather than finding one. Good point though and I hope accessing Tabbles via the extension makes it into release eventually. Would be cool.