Thanks.
There wasn't anything special.
I just copied them back to FlashFXP folder after fresh install.
Of course FlashFXP doesn't show them on startup.
I used Load Queue. It loaded them and created new queue files.
v1.43 has no problem using queue files created by v2.0.
But v2.0 has a problem using queue files created by v1.43. It keeps sending QUIT command. That's why I joked it forwards compatibility.
Thanks a lot!