Liana Ruppert “Baldur’s Gate Early Access saves will not transfer over, despite a few conflicting reports stating that it’s not confirmed. When we reached out to PR about confirmation about save transfers, we were told specifically that “Early Access saves will not transfer over when the game fully launches at a future date.” This answer is also reflected in the recently updated FAQ portion of the game’s Steam page as well.”
Source: N4G PC Baldur's Gate 3 Early Access Saves Won't Transfer Over At Launch