I've added a new page to the sidebar of this blog, where I list 26 images that occur with the episodic formula, together with the book and chapter given in the accompanying formula. Perhaps among these 26 passages we can get some good cribs.
In matching up images to gospels, XDC.D makes the most sense if we read it as Matthew, HF.HS reads best as John, and CO.IH.D works best as Luke.
I feel fairly good about those three readings now, but page 170 of the codex presents us with an interesting mystery. We have an image accompanied by the episodic formula and three scriptural references:
The three references are XDC.D=Matthew chapter 5, CO.IH.D=Luke chapter 8, and CO.I.XCAB chapter 9.
Matthew 5:15 and Luke 8:16 share in common the Parable of the Lamp under a Bushel. In Matthew, this ends with the exhortation, "Let your light so shine before men, that they may see your good works and give glory to your Father who is in heaven." I argue that the picture shows Jesus carrying a light, and the dots represent the illumination of the light.
But then what is CO.I.XCAB chapter 9? It wouldn't be Mark, because this parable is told in the 4th chapter of Mark, not the 9th. (In fact, Mark is strangely absent as a source in the episodic formulae).
Compounding the mystery is that the name of the third source begins with the same symbol as the name of Luke, and I can't find any other evangelists (canonical or otherwise) whose names start with L.