I believe the short answer is no, sorry to say.
If I’m not mistaken, the visualizer creates lines on the highway the same way the game does: the thicker dark lines are the “up” beats as marked in the BEAT track, while the lighter lines are the “down” beats. Then thinner lines are put directly between the “up” beats, which makes sense for 8th notes but not so much for triplets.
You might be able to create a triplet effect by creating triplet patterns in the BEAT track, but be aware it will also affect venue animations and OD burn rate if you use that BEAT pattern in-game.