Turning on Aerial Faith Plate trajectory display?
In Steam\steamapps\common\portal 2\portal2\maps, you can find the commentary information called sp_a2_trust_fling_commentary.txt which contains these two relevant lines:
"precommands" "developer 1;ent_bbox trigger_catapult"
"postcommands" "ent_bbox trigger_catapult;developer 0"
So, you can run developer 1 to enable developer commands and ent_bbox trigger_catapult to trigger the debugging information for the trigger_catapult entity.
Here is what happens when I do developer 1;ent_bbox trigger_catapult without triggering:
