Think of the levers themselves as limiting switches. From above idle detent to clb detent all you are doing is setting the max limit of the auto-thrust. FLX and TOGA are not used in the auto-thrust system. To disconnect you can pull the levers to idle, use the instinctive disconnect switches( 1st match the thrust lever to the current amount of thrust indicated by the TLAs-Thrust Lever Angle indicators on the EPR guage), or push the auto-thrust button on the FMA. Or, if you are really brave, you can set power yourself just like a conventional airplane.
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