Animated shapekeys/morph targets

I read in the documentation you can use morph targets for things like speech animation. I know how to trigger and mix morph targets using curves in UE4, but to me this does’t seem like the best way to do complex things like a speech animation. I would rather be able to do it in a proper animation package like Blender.

I’ve been experimenting with various things like bones and drivers to trigger the shapekeys. When I try this, in UE4 the bones move correctly but do not affect the morph targets.

I tried directly animating the shape keys but this didn’t work either.

I noticed something called ‘custom attributes’ in the import settings in UE4, which I thought might allow you to import the animated ‘custom properties’ you can create in Blender. Combined with drivers I thought that might do the trick but the properties don’t even show up anywhere in the engine so I assume I am misunderstanding what is meant by ‘custom attribute’.

Is what I’m trying to do even possible or is everything after the morph target import stage meant to be done in the editor?