I am messing around with low gravity for one of my maps and I can get the player to be affected just fine, but I can't seem to figure out how to get the cubes affected by the gravity. I have messed with all the flags on the gravity trigger but the cubes just don't want to float.

The trigger_gravity does not work for anything except the player, though it has flags. This is a known bug. Instead, place a trigger_push, direction UP, Set the flags only for physics objects and try finding the right push amount. 300/301 is no gravity, everything below will result in low gravity. I am currently doing some maps with moon gravity and ubes, and I am using 240.

I'd use a trigger_vphysics_motion instead. You can directly set the strength of gravity; use a trigger_push in conjunction with it if you want to change the direction of gravity.

Thanks for the help guys.