Gravity is inversely proportional to the distance between objects.
Do we use Euclidean distance or the invariant interval for that distance?
Using the invariant interval makes everything a bit more complex: An object that is one lightyear away, is also one year "younger" when we observe it. Does that temporal distance contribute, so that when we calculate trajectories and physical phenomena on a distance - they are different from what's observed locally?
Does this affect observed things such as the trajectory of two equally distant (from us) objects and rotational velocity of distant objects?
When we look towards the center of the milky way, we're looking about 27 000 years back in time; i.e. the temporal distance is 27000 years, and spatial distance is 27 kly
When we look at the center of the andromeda galaxy, it's about 25 Mly away. When we look at another object in the andromeda galaxy, which is also 25 Mly away - the temporal distance between those objects, relative to us is 0.
So; is the relative temporal distance between objects and the observer incorporated in Einsteins field equations?