I will soon be categorized as a “candidate” in the Catholic Church but the date is not set formally. When, in your view, would it be a good time to step down from positions on committees and attendance within the Presbyterian church? I have been on both sides of the proverbial fence for a while now.
If you have come to the conclusion that God has called you to join the Catholic Church and you have decided to follow that call, that would seem to be the time to begin severing formal ties to a previous church. As you are already in RCIA and are preparing for reception into the Church, it would seem that you are past that time and should consider devoting yourself exclusively to Catholic worship and to preparing for membership within the Catholic Church.