GMS 2 Only trigger collision event when colliding with specific collision group


Hi all.

Recently I've been working on physics collisions on multiple levels using Box2D.
To achieve that, I define each level's collision mask with a different positive collision group (>0).
When the z value passes the midway point (half level height), I unbind the player's fixture, change its collision group and rebind it.
This works perfectly when no collision event is required.

Objects that need interaction, however, require a collision event.
As a consequence, the collision event is also triggered on collision with instances of a different collision group. Which is precisely what I'm trying to avoid since they're "on a different level".

Is there any way to only trigger the collision event when colliding with fixtures that are part of a certain collision group?
It seems that once you define a collision event in an object, this overrides any collision group setting.
I especially like to avoid having to check things like:
// Object's collision event
if (level != other.level) exit;

// Further code goes here...
Basically I'd like the above if check to be implict in the underlying wiring.

Anyone who has experience with this?