Nested workers aren't shipped yet, but as of https://chromium.googlesource.com/chromium/src/+/908b82feaae2e824e32a0ec1df505fe5ba2ac671, they can be displayed in devtools.

However, in the current implementation, all workers are just displayed as a list, with no indication of ownership or ancestry. It would probably be nice to be able to see this relationship from devtools.