Well, while sphalerons theoretically break B+L in the non-perturbative regime, they are exponentially suppressed at the energy level of our colliders. At the same time, irrelevant operators that also violate it are suppressed by the GUT scale. So even if you take the minimal Standard Model at face value, you're out of luck finding any sign of the violation either way. But if Neutrinos get Majorana masses, that would be an additional explicit violation at the perturbative level. That would be something we can directly observe, as in neutrinoless double beta decay.