Yep, E-Coder (all HW versions) documentation is ... lets be polite

... unfinished. And yes, it is not even consistent and complete for ESDR2. Obviously, there is no documentation as yet for ESDR3 (due to its alpha state).
Also, there are few different HW finishing options even within same HW mainline. I do not think it is intentional, it is just what it is.
It is possible that your Coder has no indications (missing silk print) of back panel jacks:
then try to look at Coder's back - indication may be printed there:
As for LEDs. I believe currently those are functioning differently under ESDR2 and ESDR3 (on common reason).
Under current latest ESDR3 alpha, central LED (red) is TX; and left LED (green):
can be on by switching the following settings:
I have lodged feature request regarding E-Coder here, please feel free to add your suggestions:
github.com/ExpertSDR3/ExpertSDR3-BUG-TRACKER/issues/79