Hi All
I would like to agree with what @Christiaan_Huizer & @Jean_Pierre_Traets in combination mentioned above: There comes a time when the standard documentation just do not work anymore, because of one’s knowledge, the breadth of the product and the frequency of the product updates.
It also depends on what you look for in documentation:
- A description of how the tool (Excel, SAP or Coda) works, or
- A description of how to implement certain use-cases.
I am an FICO S4/HANA consultant, and we have the same problem there - SAP brings out up to three version’s of S4/HANA. Each upgrade has a release note, covering all the functionality impacted by that release. This covers finance, sales, material management, product planning and control, project management, etc, etc. To find something in SAP’s documentation is a nightmare. Add to that blogs and videos from 3rd parties, usually of extremely dubious quality…
What I have recently started doing is to use Coda to build my own “Help infrastructure”. One table is called Interesting Stuff. (Each of my SAP, Personal, and Coda docs has this table.) Every time I find an interesting video, SAP help file, blog or Wiki entry, I use the Coda Chrome extension to store the URL, and a tag(s) for the document.
This document (SAP or Coda) is now solely focused on topics of my interest. For example, I have information on product costing in a repetitive production, make to stock environment. I do not look at anything around make to order, be it make to production order, make to sales order or engineer to order.
Similarly, for Coda, I do not collect anything black magic like APIs, I stick to the basics.
If you are interested, here is the link to my FICO SAP black book Coda doc. It is currently for personal use only, but I have started tidying it up for possible public use going forward. Maybe for a fee… 
Many happy ramblings for the new year!
Rambling Pete