What is this shade loving plant please?
See the enlarged photos here.
I'm seeing two distinct plants. The last 3 pix are something different from the first set. I can't see a complete leaf of the first plant so it is hard to id but compare with images of FIlipendula rubra or Filipendula kamschatika.
Leaning more towards: Cryptotaenia canadensis
The first one isn't Cryptotaenia. Perhaps a Sanicula sp.
Can you post again when the flowers open?