BobTheBuilder

You are right, will add it. Starting to get complex, maybe need a visual decision flow chart.
Good question, need to test it. I wold probably say Grid, Battery then Gen because Gen takes a while (20-30s) to kick in.

Interesting video. I think that the Sunsynk's touchscreen interface is far better than the Sol-Ark app though, but maybe I am biased, would love to see the new Sunsynk dongle app. Hint-hint @Tariq
So let me try to get this right, second time around, edits in green red, version 1.1 1.2:
The inverter will use any source at its disposal to keep essentials, or "Load" alive, within constraints set regarding the battery in the System Mode screen, Work Mode 1 and 2 tabs; The whole System Mode screen revolves around the battery: The inverter will draw from, or charge battery to the desired SoC, at the desired time: from PV (or Grid, or Gen if ticked, and if both ticked, then in that order. Note that Grid and Gen cannot be used simultaneously, it's either one or the other) drawing from the battery, or charging the battery at the rate (W) specified in the stated power level; If Load Priority is ticked, it will use PV at the specified rate (W) to first service essential loads; and if any PV is left over, it will use the left-over PV to charge the battery (even if the battery SoC is higher than what is set); if PV is too little, or the rate (W) set too low to service essential loads, then it will draw what it needs from Grid / Battery / Gen  to supplement PV; If load priority is unticked: It will use all PV to charge battery, at the specified rate (W) (and will continue to charge past the desired SoC which is set on the timer) If Grid or Gen or both is ticked, it will use Grid or Gen (or if both ticked, then in that order) to achieve the desired SoC of the battery. Note that Grid and Gen cannot be used simultaneously, it's either one or the other; If the desired SoC is achieved for the timeslot, unlike PV it will stop using Grid / Gen to charge the battery. It does not like to waste PV. Note that battery charge / discharge rates in the timer are overridden by the values in the Battery Setup screen, Batt Type, Batt Charge and Shut Down tabs. I hope to get this right in order to help newbies, I know that I spent 3 days trying to figure it out through trial and error 🙄 So please double check me, any edits are welcome.

Actually, I think I answered most of my own question:
However, what happens if there is no grid, generator or PV during a time period with a power limit? Assuming the load exceeds the set limit. Will the inverter ignore the limit to keep the load powered?
 
The scenario I have in mind is to partially discharge the batteries once a day to keep them healthy. However, I want to do it gradually at about 0.25C. But as there are no solar panels, I am not sure exactly what will happen if load shedding occurs during this discharge interval. If there is load shedding, I would very much want the batteries to be able to discharge at the full rate allowed by the BMS.

This is a far better explanation than the user manual. The one thing I am not clear on is exactly what the 'Power' column affects. And does its behaviour change if the grid/generator checkboxes are enabled. Does it limit how much power the batteries will supply during that time period (presumably the deficit then comes from the grid/generator, or PV if available)?