There has to be an easier way to do this.
There is!
I can't find anything in the DCS Manual..
That's because you're looking in the wrong book!
From page 28 of The DCS O Gauge Companion 2nd Edition:
Selecting Engines:
• Pressing the ENG key enters the Engine List
• The Engine List displays all of the PS2 engines that are entered into the DCS
Remote by DCS ID# and name
• Engines may be either in the active or inactive portions of the list
• An engine is selected by either scrolling to it using the thumbwheel or entering its one or two digit DCS ID# using the number keys. This will highlight the engine
• If the engine is in the inactive portion of the list (below the line INACTIVE ENG),
pressing the thumbwheel selects the engine and places it in the active portion of the list
• If the engine is in the active portion of the list, pressing the thumbwheel selects the engine and returns to the Engine Control Screen
• There are three soft keys displayed above keys S1, S2 and S3
• Pressing soft key S1 (INA) will place the highlighted engine in the inactive portion of the list
• Pressing soft key S2 (S/U) enters the Engine Setup menu
• Pressing soft key S3 (ALL) select all of the active engines to be run together and
returns to the Engine Control Screen
This and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!