Watch RTX RTOS window shows five mutex objects, by default created by __main (not main() or app_main(). So far I did not explicitly create or use mutexes in my application. But after my application has started, two of these five mutexes are owned by my app_main(). Is there any documentation (or source code) of what __main() is doing ?
Those mutexes are used by the C/C++ Standard Library and are being created during __main.
If you are interested in details how they are being created and used then you can take a look at the RTX5 C/C++ Library interface functions in rtx_lib.c (_mutex_... functions).