MySQL slave_open_temp_tables always shows 1
I found the way to do this.

STOP SLAVE;
SHOW SLAVE STATUS;


write down relay_master_log_file and exec_master_log_pos

RESET SLAVE;
CHANGE MASTER TO MASTER_LOG_FILE = 'relay_master_log_file', MASTER_LOG_POS = exec_master_log_pos;
START SLAVE;


And now it reports Slave_open_temp_tables AS 0.