Hi
I actually use Node Red to control the MP2 mode, and switches to “Inverter Only” when appropriate to stop any marginal but constant grid in/out (I am using ESS, but not DESS).
Node is the VEBus System Control one, selecting the Multiplus, then the Switch Position setting as “Measurement” field.
The difference between ACinIgnore & “inverter only” are a bit technical and I am not exactly the best person to explain (I understood they do not act on the same internal relays), but at the end, they achieve the same regarding the need to “disconnect” from grid.
However, a big difference is that “inverter only” can be controlled from Node Red, while “AC Ignore” needs to go through the less flexible VE Config way. So “inverter only” is a suitable way 
Note: one interesting thing with inverter only is that even if “disconnected” from ACin, the Multiplus still probe the voltage on ACIn (which I use to monitor potential grid shutdown, to send me a warning). Unsure the ACInIgnore would allow to keep this voltage monitoring on ACIN.
Matt