Since the only Google hits for 'Steckbaum' refer to a type of educational toy (typically in the shape of a tree) with openings into which a child can place objects of various shapes, my guess is that 'Steckbaumverbindung' refers to a situation in which the various leads of a cable are fitted with separate contacts that are individually connected to their mating contacts, rather than being housed in a connector shell so that they can be connected or disconnected as a group. If this is the case, there is most likely no direct English equivalent, so you would have to use a descriptive translation (e.g. 'If the cable leads are connected individually, the screen/shield (UK/US) is connected via to a separate contact' ( or ...'connect the screen via a separate contact' if this is an instruction instead of a description).

from the ref:

Steckbaum
Holzbaum mit verschiedenen Ausschnitten, in die die richtige Holzform durchgefädelt wird. Gut für die Feinmotorik!
ab 1J.
.