I've seen this a few times in both official Cryptic missions and in Foundry missions, where the ship's scanner or a tricorder scan when used will point towards the mission objective.

How do I do set that up for an objective in Foundry? Is there a special prop that acts like a scan magnet, or a behavioral option hidden somewhere?

I dont have an answer for you, but its a great question that i would like to know myself. im sure someone here will know if its possible, and answer for us.

It will be "attracted" towards the closest object that you can interact with

This object can be interacted with either a component complete trigger or an interact with object objective

This objective waypoint is the default setting for objects and contacts in the foundry. In fact, turning it off seems to be disabled so you don't even have a choice really.

Ah, thanks! It looks like it wasn't showing up because the objective was behind a reach marker.

On the negative side, the reach marker serves the greater story purpose, so I'll have to do without the scanner waypoint compass.

On the plus side, if you ever want to turn off an objective waypoint, you can apparently do that by gating it behind a reach marker.