How do these two cards interact? Just got them together in a campaign mission thanks to Ko-Tun's ability. Can I interact with the crate the Pit Droid is carrying from 2 spaces away, or does the Pit Droid's ability requiring adjacency ignore that?

You can't interact with a carried object by default.

Useful allows adjacent heroes (includes a hero in the same space due to Companion adjacency rules) to interact with a crate being carried by the Pit Droid.

Grappler Arm allows to interact with objects within 2 spaces.

If the hero is not adjacent, Useful does not allow the interact, so Grappler Arm doesn't have an object you could interact with even when the hero is within 2 spaces of the Pit Droid.

Also, the hero is never within 2 spaces of the carried crate even when the hero is within 2 spaces of the Pit Droid. (There is no distance defined for carried tokens/objects.)

So, I'm pretty sure Grappler Arm doesn't help.

I'd agree with a1bert based on the strict reading of the wording on Useful.

I agree with a1bert’s interpretation 100%, but I think I would allow the heroes to do it anyway. I feel that the intent of the Grappler Arm is to override the adjacency requirement when interacting, so it seems silly to tell them “no” especially given the rarity of the situation.

We just went with it for thematic reasons, but I agree with Albert's reasoning.