Change Collision size through triggers

[Chewii]

The title says it all. Is it possible to do this? And if so, how?

 

[Ezekiel12]

Depends on what exactly you want. Collision size and pathing (square) are two different things.

If you want to turn the pathing on/off you can use Unit -> Turn Collision On/Off.
(Or windwalk/ghost ability for partial solutions)

To change the collision size value in object editor, you would have to use a passive transformation.