Is Slovakian unique in having "long/short consonantal vowels"

It seems to me that Serbian has at least one consonant that functions as described above. In Serbian:

Serbian is српски
Croation is хрватски

Russian puts a vowel before each of those r's.

Pronouncing things over to myself, I'm not sure English doesn't have vocalic consonants, in cases like the middle syllable of cummerbund and bubblegum. We don't spell them without letters for vowels, but I would want to look at (and be able to read) a spectrograph before saying that there was a pure vowel before the r or the l as the words are normally pronounced.

NA, the question wasn't whether other languages have vocalic consonants, it was whether any of those languages distinguishes long and short vocalic consonants as does Slovakian.

cummerbund and bubblegum

The first one doesn't work in a non-rhotic accent. But certainly in my accent bubblegum works. And indeed bubble and best of all bubbled. Now you point it out, I don't really see why as a matter of pronunciation they are materially different from the same kind of sound as they have in vlk. So probably this is just a matter of orthography - the Slovak orthography is unusual, but in reality doesn't reflect sounds that are that unusual.

What about Bulgarian? They use the hard sign ъ as in България

The usual English example is the kk in bookkeeper. Contrast with bookcase.

English doesn't have long and short vocalic consonants, though, iviehoff.

English doesn't have long and short vocalic consonants, though, iviehoff.

Certainly not orthographically. But I find that the L is longer in bottled than in bottle when I say it. So if we take it as matter of pronunciation rather than orthography, I wonder if maybe I have found the same thing. But I'm not sure. What do you think?

If I understand correctly, the distinction in Slovakian is phonemic, that is, there could be a difference in meaning between two words that were identical except that a vocalic l or r was long in one and short in the other.

To the extent there is a difference in length between the last syllable of bottled and bottle, it depends on the environment, that is, a following consonant makes the l longer. So there is no phonemic difference. If you pronounce "bubbled" with the second vowel having exactly the length it has in "bubble", everyone will understand you to be saying "bubbled" (although perhaps a little oddly). But if I understand correctly about Slovakian, that wouldn't be true in the case of a pair of words that differed only in the length of the vocalic consonant; pronounce the one with the long consonant shortly (so to speak), and you will be understood to have said the other one.

There's no phonological reason for English not to have this distinction. Imagine that a small bottle can be called a "bottle-ling". This would not sound the same as "bottling".
Perhaps somebody can come up with a less contrived example.

I think English would very soon reduce bottle-ling to bottling. In any case I think I would analyze the le-l bit of bottle-ling as a vocalic l followed by a consonantal l, not as a long vocalic l.

I seem to have switched from "bottled" to "bubbled" in #17 without meaning to. Either one would do but I should have stuck to one or the other.