Core answer: the blue scent trail is treated as Logan's sense power, not a HUD assist, so it stays on during tracking. What you can do today is install the hotfix that makes trails less loud, and strip the extra hand-holding around it.

What Is Actually Controllable

1Install the Hotfix First

2Kill the Extra Guides

Open Settings → Accessibility / HUD / Gameplay Assists and turn off the overlays that stack on top of the scent trail.

Why this order: most "I turned everything off and the gas is still there" reports happen because people only flipped Navigation Assist and assumed that was scent. It isn't.

3Know When the Trail Can Appear

Decision Points

You wantDo this
Least UI possible todayHotfix + Mission Waypoints Off + Navigation Assist Off
Still need a hint sometimesMission Waypoints set to R3 Hint, Navigation Assist Off
Maximum guidanceWaypoints On, but do not also turn Navigation Assist On
No scent at allNot available yet. Wait for the toggle under exploration
Choose R3 Hint if your real complaint is "always-on yellow arrow," not the scent itself. A lot of the stacked-HUD look comes from leaving every assist at default.

Common Mistakes to Avoid

After the hotfix, the trail reads as a thinner ground wash instead of a thick neon tube. It still points the way. If a full toggle ships later, it will almost certainly live in the same Accessibility / HUD list. Check that menu after every update.