Potential uses is something different than a question of embedding.
What answer are you looking for ?
node-red runs on nodejs, if you can embed nodejs in a java application, you can probably do it (albeit with a lot of work)
If you want to know what node-red can be used for, this covers a wide range, but if you have one application/hardware and you want them to talk to some other application/hardware (and they currently can't) - node-red can help. See it as a "glue" between hardware/software.
Last year there was a survey, which may be of interest.
