...
VirtualThreads.allThreads() (and JDWP VirtualMachine/AllThreads) enumerates all active platform threads, virtual threads are not enumerated.
For thread dumps and troubleshooting purposes, the debugger can invoke com.sun.management.Threads.virtualThreads() to obtain a stream of Thread objects for the virtual threads. This can be used as stop-gap solution until there is better support for structured debugger in the debugging APIs.
Thread groups
Virtual threads are not active members of a thread group.
...
Overview
Content Tools
ThemeBuilder