I don't think that it is. The reason that I found the Safari debug menu was that I was hunting for a hidden tab preference. It ain't there, or if it is, Safari never tried to access it.

It makes sense that there's no hidden tab settings because, according to some other thread that I'm way too lazy to search for, the version of KHTML that Safari is based on doesn't include tab support; it was added in a later version, after Apple had forked.

This is a bummer, because as cool as Safari is, without tabs or an equivalent feature, I ain't using it. They just increase my productivity way too much for me to give 'em up. I could live without my bookmark shortcuts (gg for google, az for amazon, etc.), but not without tabs.

I'm totally confident that Apple will add some sort of tab metaphore in the future. The demand seems to be huge.