If Pelosi refuses to submit the articles of impeachment to the Senate, McConnell can convene the Senate anyway, summon the Chief Justice, and swear in the Senators as jurors. Democrats can boycott, but they can’t stop the trial.
McConnell can then propose to dismiss the charges or even hold a vote to acquit the president.
Pelosi can hide the articles of impeachment in Adam Schiff’s basement forever, and it won’t make a bit of difference.
Case closed.