The research for improving the production of other kinds of vitamins is more active, by trying to either discover or create bacterial strains suitable for this purpose.
A serious problem is that unlike the production of traditional food, the production of vitamins and nutritional supplements is concentrated in a few countries, and mostly in China.
So if overnight everybody would become vegan, then suddenly most of the world would become nutritionally dependent on China.
Ideally every bigger city should be able to produce the vitamins needed by its inhabitants, like it is able to produce other staple foods, but we are very far from this when entire countries may not have any vitamin production facility.
Humans also produce creatine, choline and taurine, but for these three there is convincing evidence that the internal production is not sufficient, so for vegans it is beneficial to take supplements with them.
It is likely that the internal production of K2 is also insufficient, but I have not seen yet any conclusive research results about this, because it is very difficult to control all confounding factors.
Even if it is not certain that this is needed, it is prudent for vegans to also take vitamin K2 supplements, along with the other substances known to be missing or insufficient in vegetables (vitamins B12, D3 and K2; DHA and EPA; creatine, choline and taurine; iodine, selenium, calcium and sodium).