I don’t doubt Putin wants to restore Russian borders to a Soviet era. Invading might overstretch his forces. Like I said before, one on one with Ukraine, Russia has advantages. Fighting on multiple fronts is different.
However, he could try to destabilize Balkan countries to weaken them within. I don’t know the current tensions of every single country but we all know ethnic tensions have led to genocide in that part of the world.
A destabilized country would be easier to invade or at the very least tie up other NATO members. How Russia could go about doing this is another discussion.