I did a quick search and found this:
Interposed between the battery and inverter, it looks as if this might allow you to drop the voltage and convince the inverter to reduce its output power.
Control by a knob obviously won’t work (except maybe to establish whether it’s worth putting more effort into the idea and developing the control strategy and implementing it), but the “efficiency … up to 94%” caught my eye. In other words, you’re guaranteed losses of worse than 6%, and that’s on top of the inverter losses.
It’s not making a lot of sense.