Keying Sequencer FX System Toggle track via scripting

I’m creating an Editor Utility Tool that adds FX tracks to sequencer.
I have had success with adding a Niagara System Life Cycle Track with in/out points but I’m having difficulty with keying FX System Toggle tracks for Cascade from blueprints.

Here is where I’m at so far with doing that:

This adds the particle and the FX Toggle Track like so:

However, I can’t find a way to add keys to the FX Toggle Track

The usual way I would add keys is via the channel (top nodes in BP pic as example). However, the MovieSceneParticleSection doesn’t have any channels (length 0). There are not blueprint nodes to add a channel and I haven’t been able to add keys further up the chain.

How do I key the FX System Toggle track via scripting?

For anyone who finds this is future, I got a reply from Epic via UDN:
“We don’t currently support particle channels in scripting (see UMovieSceneSectionExtensions::GetChannels). You could potentially modify it to support particle channels, and just return their byte channel representation.”