If I send a TonePrint to my Corona Chorus with the toggle switch set to "Chorus" position (upper position) or to "Tri Cho" position (lower position) instead of "TonePrint" position (middle position) do I will erase current settings for "Chorus" or "Tri Cho" with the new parameters of the TonePrint I send to the pedal?
No worries, you can consider the "Chorus" and "Tri Cho" position as presets that cannot be altered.
Of course it still possible to change the knobs position on the pedal alter the sound of the selected preset. But if you want to store a TonePrint in the pedal, this one will be stored only to the TonePrint slot (middle position) and not on the the Chorus or Tri Cho position. Keep in mind, no matter what setting you are using, the preset will always reflect the position of the control knobs.