How tall are these seedlings, how easy to handle without damage?

An inch apart isn't bad for a short while as the roots won't begin to entangle themselves right way when spaced like that.

Once they get to a comfortable working-with size then just carefully dump out the soil container onto a workspace and gently seprate the seedlings and transplant them. With many things that is usually when true leaves develop.

You might ask over on the Trees forum if anyone has done this as tree seeds are quite different and much slower in their development that are flowers and vegetables.

Dave

Use water to separate roots. You should see what growing hydroponics is like. The roots just slide right out from each other