This still isn’t working, and I’ve figured out why: the motion of the platform is on a timeline linked to a spline, the event graph sets the world transform on the update node of the timeline. The players motion is inherent from the teleporting (every frame I suppose) of the platform, as upon printing the player’s or the platform’s velocity, it shows 0,0,0 (unless the player moves using input).
Your solution seems logical and I see no reason why it won’t work if the platform actually moves so I’ll mark it as the answer.
I’ll see if I can rework the platform motion to suit this answer 
For anyone looking at this answer, it isn’t compatible with teleportation based motion such as “SetWorldTransform” on things that are comparable to a Tick, a workaround is below
I worked around this (without altering my spline/timeline pathing) by getting the forward vector of the platform’s current rotation, multiplying it by the platform’s speed (in units per second) and using that as the Inherited Velocity, the rest is thanks to you.
In my example picture below my platform’s speed is determined by a float handle tied to the Timeline where 1.0 is equal to that 100,000 units every minute, hence the multiplication of the “Train Speed” prior to multiplying by the ForwardVector by a factor of 1667.
