The rules say this about the resolving ship's phase - Phase 1 - as an option:
Abandon this Port's Cargo to the competition by removing his Ship and taking his coins back into his Safe. Important: By doing so, the player forfeits any chance to get
this Cargo (unless other players keep the competition
alive for another turn). He is not allowed to send ships
back to this Port when redeploying his ships during Phase
3 of this turn, though he may still do so in later turns.
We've only played a couple of times, but found that during step 2 (trading in for goods) we forgot which ports were backed out of a couple of times (during prolonged step 2 calcluating). I realize it only really matters if someone has a Syndicate card and got two coins for backing out. But there's a little memory element in play to keep them from accidentally going back to the same port in step 3.
Can anyone suggest a good method of marking a port that was abandoned?