That’s a good point, we do not actively export single properties via bpmn-js-properties-panel, which is kind of a breaking change comparing it with the 0.x versions, and makes composition of existing properties pretty hard.
I created an issue for this to start a discussion whether this capability should be re-added or not: Export individual properties and entries · Issue #720 · bpmn-io/bpmn-js-properties-panel · GitHub
In the meanwhile, you could also copy the conditional props and the needed helpers. I did this by example and used the props in a custom properties provider: properties panel custom conditional props - CodeSandbox