You can open a stream using:
uvm_default_recorder.create_stream("stream_name", "TVM", get_full_name());
This opens a stream and shows it under the component you call the code from. You can do this some time before the run phase (start of simualation, end of elaboration, it doesn’t really matter). If you load your waves after the UVM hierarchy was created, you’ll see the stream there.
I’ve no idea what “TVM” means, I just looked around at what begin_tr does and at some point it calls this function with “TVM” as an argument.
After you’ve opened your stream, make sure to use the same name for calls to begin_tr.