G'day. You asked for personal preferences for descriptions, so mine:

<L-CC-<L-CC-<L
<L-CC-L>-L>

locomotives are "<L" or "L>" to indicate direction.
locomotives attach to things with a "-" between them, including other locomotives.
carriages are marked with "C", one per.

if you felt extra fancy, "C"argo, "F"luid, and "A"rtillery wagons instead of just "C"arriages would work out too. (optionally, the first letter of their name or something, for mod support.)

Yes, I also saw this notation somewhere. Yet I decided to wait for a chance (to ask someone like you) to know more info before implementing.
So it seems "-" is used between every groups. Then I realize in your second example, where you also use "-" between two consecutive locomotives of the same direction. So is it an exception rule?
Here are three example train, to see if my "interpretation" is correct or not:

A/ LCCCCL

<L-CCCC-L>

B/ LCCCCFFCCCCL

<L-CCCC-FF-CCCC-L>

C/ LLLCCCCCCCC

<L-<L-<L-CCCCCCCC

The carriage symbols "L", "C", "F", "A", "V" are already implemented, in case you have not realized them yet. They are all mentioned on FAQ page.

Ah, I thought it was used to show "connection between different types of things", and "<L<L<L-CCCC" looks a bit odd to me compared to "<L-<L-<L-CCCC", but either one works fine. So, uh, your call I guess?

I didn't notice, that, indeed. The FAQ is comprehensive which is great, and I'm sure i missed some other stuff too. :)

I see your point.
I am thinking of breaking down the different components into a few options, so either can be picked (as it is a matter of personal taste anyway, not right-or-wrong):
- Locomotive direction: Same ("L", "L"), Pointy ("<L", "L>"), Case ("L", "l")
- Connection: None, Between groups, Between groups and each locomotive
- Notation: Explicit, Group, Short
- etc.

So the preference you requested would be "Explicit Notation" + "Connection between groups and each locomotive" + "Pointy".
I guess that would be more flexible. (Though I probably have to expand FAQ to describe a few combination examples.)

The new options are implemented in recent release 0.17.1 / 0.18.1.
You need to set following options to achieve the representation you have described:
- Notation: Explicit Notation
- Locomotive direction: Pointer (Wrapping)
- Connection sign position: Between groups or Locomotives

Yet you may play around with the settings. The FAQ is updated to show some examples.