Do you mean, add an actual MIDI pitchbend, or just a symbol?
No, for the former.. as with any controller, you would need to stipulate a length. (The only controller with variable length that can be inserted into the Score Editor would be done via the crescendo/decrescendo "scissors" when used as Dynamics Mapping, and you'd have to set that up in the Key Editor first anyways
As regards symbols, however, there are a couple of diagonals and "falls" that may give you what you are looking for (but they are of course purely "graphic").
Mac Pro Quad-Core 2.66 gHz | 16GB RAM | MOTU PCI-424/2408mk3|MOTU Midi Timepiece AV l Mac OS X 10.8.5 l Mac OS X 10.6.8 | Cubase 7.5.20| Cubase 7.0.7| Cubase 6.5.5 | Cubase 5.5.3