Does the BL600 support the UartBREAK command? If not, how can I emulate this command (maybe through GPIO)?

UartBreak() is not supported by the chipset used in the BL600, but it is in smartBASIC. However, a workaround for the BL600 would be to use a spare SIO digital output on the BL600 then feed that to an AND gate and make the other input for the AND gate be UART_TX. On start-up of the module/program, set that digital output to high. If you want to “issue a BREAK” just set that digital output to low. As a result, the output of the AND gate will be low as long as that input is low. Otherwise if it is held high, the output of the AND gate will be identical to the state of UART_TX.

The above method is essentially a way to simulate a BREAK in the UART by toggling SIO pins high/low that are tied to UART_TX.