Could a Royal Navy break-in to the Baltic supply Russia and conduct coastal demonstrations?
Short answerYes, but the larger effect would be severing Germany's Scandinavian supplies and tightening the blockade enough to threaten collapse within weeks.
NotesOpening a supply route to Russia would be useful, but the decisive effect lies elsewhere. A British fleet in the Baltic could close Scandinavian trade and tighten the blockade around Germany after defeating the High Seas Fleet. Russian resupply and coastal demonstrations would add pressure. The loss of Scandinavian imports could produce a German economic crisis within weeks.