I've been trying to re create this kind of routing in Cubase

So this is a super cool ambient effect which requires a feedback loop routing.

I’ve tried with FX channels, Group Channels and the direct routing options and can’t quite get it to work.

Any ideas?

You should be able to do it using a cable, as Cubase doesn’t know what you plug in what in/out. If you have channels enough just make permanent loop that you can use when the mood strikes.
Don’t know if there are delays using sidechain for that effect, could be. There are certainly delays that incorporate filters in the feedback, like tape style delays. That would be another great use for a feedback loop, using your favorite distortion/bit crusher.