How to perform a bus assignment with a sub-bus element?

For convenience, I'd like to be able to do something like what is pasted in the below picture.

Sadly, this throws the following error.

Because of this, I have to do the below. In this example, it doesn't look too inconvenient, but if there are hundreds of signals within multiple layers of buses, breaking out every individual signal becomes a significant pain! Is there any efficient way to reassign a whole subbus?