Mitch McConnell is a man with an agenda. When Trump was busy cutting taxes and appointing conservative judges, the two were enthusiastic partners. Otherwise, McConnell was careful not to provoke him, but he mostly ignored him. Trumpian outrages were met with silence or masterly equivocation. Whether you took that as assent or objection was up to you.
You can be certain that Trump will be demanding unceasing resistance to the new administration from GOP members of Congress after January 20. How will McConnell respond? In the same way as before. He will brush off Trump’s comments politely and do exactly what he thinks is necessary to regain power, which, in most cases, will not involve following the Trumpian line.