Abbot Suger exalted what part of the Gothic cathedrals as a medium that filtered the light of divine truth?

Stained Glass.

Explanation:

Abbot Suger was a French abbot who is entitled to be an originator of Gothic architecture. He, also, worked as an adviser for King Louis VI and Louis VII. When Suger was in his fifties, in 1137, he decided to reconstruct the church of Saint Dennis. He reconstructed the Church of Saint Dennis combining the three architectural innovations. One of them was the stained glass windows.

The part of the Gothic Cathedrals that Abbot Suger exalted was the stained glass. This was used to symbolize the light of divine truth, that represented Jesus Christ.

So, the correct answer is Stained Glass.