Is this possible?
I’m sequencing an object with a path track bound to a spline. If I add a transform track, and delete the location, the rotation becomes 100% keyed instead of influenced by the spline.
Is there a way in sequencer to add, I don’t know, relative rotation?
One of the ways to achieve this is to use an intermediate attachment object. In the attached screenshot, the spline is in the NewBlueprint. A cube (the intermediate object in this case) is attached to the spline in the NewBlueprint. The actual object - the Cone is the attached to the Cube and relative keys are set on the Cone transform track.
Ah, yes of course, thank you! This is exactly like when you use helper objects in Max as pivot points. I didn’t think of this since there’s no “empty” object in Unreal like there is in Max/Blender/Unity.
When you say “attach”, do you mean at Blueprint component level or just parenting in the outliner? (Or one can do either, I’m guessing.)
EDIT: Turns out I already did this to begin with, since I had a bug where in the sequencer, my object was rotated 90 degrees compared to the same object animated on the same spline in a blueprint, hah! I just didn’t know how to “reach” the object on a component level, so I’m going to try via the outliner now.
Maybe use the empty actor.
And at the very top of the list too, whoops! Thank you for pointing out the obvious to me. Not sure how I missed that. 
@Max.Chen Oh! I think I know why I was confused about empty objects. You can’t add them in a Blueprint? Only to a level? Why is that? (Off topic question, perhaps.)
EDIT: Is this why the Datasmith team have such difficulties creating Blueprints from their imports? Because they rely on empty actors to represent each assembly and sub-assembly of CAD imports?