So it's that time again - time to move the tomato plants from the little seedling cells into seedling pots. I'm especially careful when doing this since I only minimally thin the tomatoes - I only remove the ones that are significantly smaller than the rest. For any of the other cells, I very carefully separate each tomato plant and transplant them each separately into larger pots. It's rare that I lose one when I do that, but it happens occasionally. I still end up with way more plants doing this than if I were to only select one per cell. But it also means that I end up with a lot of tomatoes - about 7 trays worth this time.
The key is being very, very careful with the roots. Massage the ball of dirt and roots gently and then carefully separate each tomato by holding the plant and gently wiggling it away from the others. Then you can plant each one of them. You might break a few plants when doing this, but once you get the hang of it you'll end up with more plants than if you saved one per cell.