The position of the Chief of the Boat (COB) comes from the real world title typically seen aboard U.S. Navy submarines. The COB’s primary role is to serve as the senior enlisted advisor to the Commanding Officer (CO) and Executive Officer (XO). Like in the real world, the COB is typically the most senior enlisted officer, but can be assigned to a lower-ranked enlisted officer, and does not necessarily change hands if a more senior enlisted officer comes aboard. This makes the position outside of the direct chain of command, while still imparting a good deal of responsibility.
In Star Trek Adventures, Players can select this role like any others they have access to. Doing so imparts the following Role Ability:
Once per scene, the COB may spend 1 Momentum to Create an Advantage (instead of the usual 2) for a Task they are assisting with. This Advantage should represent the COB’s command over the ship’s Enlisted personnel that may have additional insight/abilities for the Task at hand.
This may sound similar to the Chief Engineer and Chief Medical Officer (CMO) Role Abilities which grant them free Advantages. Unlike those, which only take effect in Main Engineering and Sickbay (respectively), the COB’s advantage can take place almost anywhere on the ship. This provides a powerful utility and plenty of roleplay possibilities. A good example is having the CMO take the COB Role Ability instead of the CMO one. This would give an Enlisted Officer both an advisory position outside of medical matters, as well as giving them the power to relieve higher-ranking Officers of duty (on medical grounds). It certainly will get them out of Sickbay one way or another!
There is no such thing as an enlisted officer. The Command Master Chief, or occasionally Command Senior Chief, is the Senior Enlisted Leader. Shore Commands have a Senior Enlisted Advisor.
They are part of the chain of command, not separate from it.