Enes,
What you propose is correct I think, but you should always verify.
You can open the var/airframes/<ac-name>/generated/airframe.h file to see if the change worked out ok (assuming it compiled).
In that header file, you should notice the defines for the servo:
#define SERVO_FRONT 0
and then later on
In the conf/airframes/examples directory you have example multirotor configurations, see See quadrotor_m_2_pwm_spektrum.xml.
They use "motor_mixing" configuration sections and also use indexes into the "commands array. You can change the order there.
I haven't been able to look into how this works in detail yet.
From what I interpret here, this quad uses a + configuration, hence front/back/etc. For x configs this would be different.
<command_laws>
<call fun="motor_mixing_run(autopilot_motors_on,FALSE,values)"/>
<set servo="FRONT" value="motor_mixing.commands[0]"/>
<set servo="BACK" value="motor_mixing.commands[1]"/>
<set servo="RIGHT" value="motor_mixing.commands[2]"/>
<set servo="LEFT" value="motor_mixing.commands[3]"/>
</command_laws>
<subsystem name="motor_mixing"/>
<subsystem name="actuators" type="pwm">
<define name="SERVO_HZ" value="400"/>
<!--define name="USE_SERVOS_7AND8"/-->
</subsystem>
<servos driver="Pwm">
<servo name="FRONT" no="0" min="1000" neutral="1100" max="1900"/>
<servo name="BACK" no="1" min="1000" neutral="1100" max="1900"/>
<servo name="RIGHT" no="2" min="1000" neutral="1100" max="1900"/>
<servo name="LEFT" no="3" min="1000" neutral="1100" max="1900"/>
</servos>
<section name="MIXING" prefix="MOTOR_MIXING_">
<define name="TRIM_ROLL" value="0"/>
<define name="TRIM_PITCH" value="0"/>
<define name="TRIM_YAW" value="0"/>
<define name="NB_MOTOR" value="4"/>
<define name="SCALE" value="256"/>
<!-- front/back turning CW, right/left CCW -->
<define name="ROLL_COEF" value="{ 0, 0, -256, 256 }"/>
<define name="PITCH_COEF" value="{ 256, -256, 0, 0 }"/>
<define name="YAW_COEF" value="{ -256, -256, 256, 256 }"/>
<define name="THRUST_COEF" value="{ 256, 256, 256, 256 }"/>
</section>