You know, I had been looking at this before when it come up in the context of trying to justify extra RC doctrines that were supposedly passed on through the big "T" (Tradition) and one of the typical power grabs would be for that "books verse". They might point to the verse and say, look, see? Jesus did so many others things that the world couldnt contain the books should they all be written. But pointing that out was really in the context of seeking to justify these extra teachings (not in the scripture) or confirmed by them.
I see where it speaks more specifically there of what Jesus DID (not said) and I wouldnt doubt that because he would be the same yesterday, today and forever.
Although Jesus did things in secret (or they were just not written, whether they were done within the presence of his disciples or outside their presence) he did say he did not say anything in secret.
Luke writes of both what Jesus began to do and to teach
Acts 1:1 The former treatise have I made, O Theophilus, of all that Jesus both began to do and to teach.
So I was looking at the many other things Jesus did and said, or that he did do and did teach (as they might be mentioned in that manner)
For example here, it speaks of other "signs" Jesus did not written
John 20:29 Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
And then goes onto say,
John 20:30 And many other signs truly did Jesus in the presence of his disciples, which are not written in this book: (and so there were other things he had done in their presence not written down in Johns book)
But these are written for this purpose
John 20:31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.
And John also records what his disciples did not see Jesus doing (which was outside their presence)
For example here,
John 7:3 His brethren therefore said unto him, Depart hence, and go into Judaea, that thy disciples also may see the works that thou doest.
There is what Jesus DID in the presence of his disciples (which were not written down) and the things Jesus DID outside of his disciples presence (which were also not written down) as he did things in secret (like when he went to up the feast, he did so in secret) but thats not a secret to us (because that was disclosed). And when he was being examined he stated he said nothing in secret John 18:20
As his brethren point out his disciples are not with him here (doing things outside of their presence)
John 7:4 For there is no man that doeth any thing in secret, and he himself seeketh to be known openly. If thou do these things, shew thyself to the world.
Even here it says,
John 21:25 And there are also many other things which Jesus did, the which, if they should be written every one,I suppose that even the world itself could not contain the books that should be written. Amen.
Which would make sense according to both of these scenarios combined given the number of lives touched.
Then this one
John 18:20 Jesus answered him, I spake openly to the world; I ever taught in the synagogue, and in the temple, whither the Jews always resort; and in secret have I said nothing.
So he stated he said nothing in secret. Then he gave them the words given him (to them) saying
John 17:8 For I have given unto them the words which thou gavest me; and they have received them, and have known surely that I came out from thee, and they have believed that thou didst send me.
And these words include (within it) the knowlegde of what was not written (of the other things which Jesus did) and his words that in secret he said nothing.
The second verse
Ecc 12:11 The words of the wise are as goads, and as nails fastened by the masters of assemblies, which are given from one shepherd. (John 17:8, Dueteronomy 18:18 -19, John 5:47, John 12:49, John 17:8, Acts 7:37, Hebrews 3:5 )
Ecc 12:12 And further, by these, my son, be admonished: of making many books there is no end; and much study is a weariness of the flesh. (So then John 21:25 would confirm this one to the end also)
So I was looking at "many other things Jesus did" some of which were in the presence of the disciples others not but that Jesus also stated that he said nothing in secret. Besides, he could speak openly and others could have have ears and not hear any way, but I thought that was helpful to me in that other conversation when someone might be selling you a bill of goods. Its probably not here or there I guess, just something that had interested me