OK, In our (single volume) the basic logic behind the CLB CON button is in the Mode control panel section, "Autopilot Flight Director IAS/Mach Controls" (section 4.10 in our issue), but there's not much detail.
All the other engine out stuff is covered in "autoflight" or "autothrottle" sections. TBH the CLB CON switch that doesn't get used much in normal ops or even in event of an engine failure. I wouldn't lose too much sleep at this stage over what it does and it's functioning is often better explained/understood in the sim or fixed base trainer than in the FCOM...