Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book.
John has made a selection from all the signs Jesus did and all the words He spoke, including all that met his purposes in writing this gospel and leaving out those that didn’t. Karl Heim thinks this significant because you would collect everything you could about a dead prophet because it is all that you have of him, but you only need to tell enough of a living person to introduce your readers to Him. Then they can find out all they want from that Person Himself. John doesn’t need to tell all that he knows about Jesus because Christ is still alive.
Jesus did many signs while on this earth. He made sure that there was an over-abundance of evidence and of witnesses. This was true of His ministry (John 2:23, 4:45, 12:37) and of His resurrection (Acts 1:3, 10:41, 1 Cor 15:5-7). The gospel writers could pick and choose from the pile of evidence. Note that there was another reason for not writing everything: all that was needed was enough for the Holy Spirit to take and apply to men’s hearts.
John 2:23 Now while he was in Jerusalem at the Passover Feast, many people saw the miraculous signs he was doing and believed in his name.
John 4:45 When he arrived in Galilee, the Galileans welcomed him. They had seen all that he had done in Jerusalem at the Passover Feast, for they also had been there.
John 12:37 Even after Jesus had done all these miraculous signs in their presence, they still would not believe in him.
Acts 1:3 After his suffering, he showed himself to these men and gave many convincing proofs that he was alive. He appeared to them over a period of forty days and spoke about the kingdom of God.
Acts 10:41 He was not seen by all the people, but by witnesses whom God had already chosen—by us who ate and drank with him after he rose from the dead.
1 Corinthians 15:5-7 and that he appeared to Peter, and then to the Twelve. After that, he appeared to more than five hundred of the brothers at the same time, most of whom are still living, though some have fallen asleep. Then he appeared to James, then to all the apostles,