I don't have any tips. Just more questions: How do you document cables efficiently and easy to understand?

Obvious answers would be: my favourite CAD program, Excel, Visio/Inkscape, Paint, special cable doc software, ... 

I used to work at a company, where the 1st correct cable was put on the copy machine and scanned for documentation. 

When I worked at Chrysler, I learned a nice way to document cables using this technique:

1) Have a picture of the end of the connector and label the connector with part number and manufacturer.

2) Label what end of the connector your picture is looking at, pin side or solder side

3) Label picture pins or sockets end, pin part number or socket part number

4)  For each connector add a matrix table of pins to the picture listing the following

-  Connector name, pin name, pin number, wire AWG/part number, wire color, wire length, Other end connector name, Other end pin number

5) There may be other items on the cable to list including splices, tape areas, loom or other covering, inline fuses or fuse wire, etc.

It takes time to document, but it's nice to have later on when diagnosing problems.

I store any cable docs in the project design directory and I have a subdirectory for datasheets. Pinouts are usually on the schematic or in a spreadsheet that lists part numbers, pin numbers, function and connectivity. I don't generally need photos since I generally use my standard techniques to build cables and nobody else is ever involved.

It depends on the cable and to what use it will be put. At the small end, vintage record players where the cartridge connects to the electronics using extremely thin extremely flexible cables, often screened. The cores, of which there are usually two or four, are even more extremely thin. Colour coding varies from manufacturer to manufacturer. Soldering is tricky because the heat travels up from the stripped end to the insulation very quickly, and the insulation melts very easily. Taking too long to solder the screen will often result in all the cores and the screen melting together. The wiring between heads and electronics in vintage tape recorders poses similar problems.

At the other extreme there are RF screened cables 0.75" in diameter with a semi-hollow PTFE spacer between core and screen. I use them for aerial connections as part of my Amateur Radio interest, luckily I have not needed many! Waterproofing can be a problem. The core is often solid copper and the PTFE spacer is very difficult to cut using normal hand tools. If it cuts easily then it may not be PTFE. The screen is usually braided very tightly. I sometimes think a gas blow-torch would be the right tool for the soldering but I have not tried that yet. Over-bending the cables is a) not approved of because a bend is an inductor, and b) because the cable is very stiff and kinking is not allowed. Connectors are usually huge versions of BNC or huge versions of  PL259 / SO239 pairs.

Making cables for other things, often one-offs, depends on so many variables. I like IDC for ribbon cables and use a bench-mounted vice as a crimping tool. From years ago I have mainly used DIN or Phono (aka RCA) connectors for audio leads, as well as 0.25", 3.5mm, and 2.5mm jacks, all the usual stuff. In times of sheer desperation I have used the short lengths of wire from such things as off-cuts from resistors and capacitors as pins for connecting short lengths of flexible wire to experimenter's boards, and so on.

Going down another road there are screw terminals that can be soldered to PCB's or screwed to enclosures, spade and bullet  connectors as used in vehicle electrics, 13A mains plug and socket(s) extension cables, there's no end to it.  

I used to use IDC ribbon cables a lot. I'm not sure why they have declined in popularity.

I also used IDC ribbon on D sub connectors.

Similarly card edge connectors seem to be declining as well.

One of my first jobs as an electronics technician was to make dozens of cable for a power distribution system.

All had to be hand soldered, which took days.

The modern methods are much easier to use, but none of my cales failed.

I really like to use the crimp ferrules on wires that are getting inserted into screw terminals.  And old AMP IDC connectors are really nice, even if I don't have your fancy gun, only the T-handle tool (which is not so easy to use).

Thanks for sharing your thoughts on cables.

Once you try crimp ferrules (bootlace connectors) it is tough to go back. I am still looking for a good source (read cheap) that are simple metal tubes - no plastic sleeve.

Size? Quantity?

Farnell here sell the Knipex 97 99 910 assorted box quite cheaply

https://www.knipex.com/en-uk/products/cable-connectors/assortment-boxes-with-non-insulated-wire-ferrules/assortment-boxes-non-insulated-wire-ferrules/9799910?v=89312  

https://uk.farnell.com/knipex/97-99-910/ferrule-terminal-kit-w-box-1000pc/dp/2859404

You get more than the similar Multicomp Pro box for a similar price. (1900 vs 400)

https://uk.farnell.com/multicomp/xrbox5-en-ea481/ferrule-kit-uninsulated-5-types/dp/1734784

Not sure if Newark do the same.

I posted a picture of the Multicomp Pro ones in use here a week or so ago:

/products/roadtest/rv/roadtest_reviews/58/knipex_self_adjustin?CommentId=2cb69922-5f0d-4538-a986-2d430b0fc9cd