I've searched the web on this and found various recommendations, but not
real clarity on what is to be done and when.

I have a nice Helleborus foetidissimus plant by the doorstep. Mindful of how
poorly hellebore seeds handle (and not having time to fuss over them), last
year I let it go to seed and just dropped the flower-stalk next to the
plant. Now (just as it's come into bloom for this year, in Zone 6), there
are a couple of dozen two-leaf seedlings coming up, all close together where
the stalk was. My questions a do I let them grow for a while where they
are? how long? do I thin them? or, can I keep all of them by digging up the
clump and carefully separating - when? I have plenty of places to put them,
but would like them to survive. So the objective is to separate/transplant
them when survival chances are optimal. I understand they don't transplant
well. But they are very crowded.