Describe the solution you'd like
So that players can ''tag'' veins from surface rocks by creating a JourneyMap waypoint with proper vein name and the waypoint color same as the material's

Would be better with a custom icon, just like what Mineral Tracker mod does.

Let's leave that task to addon devs. I don't think this belongs to GregTech itself.
Good feature though, would love to see it in 1.12.