Simultaneous petrol/battery power supply

Currently, the engine runs on battery or gasoline, depending on the selected mode, but it runs on battery power until a preset threshold is reached, after which the internal combustion engine kicks in. It would be convenient to have a custom mode that allows you to choose the battery percentage to use. For example, if I have to travel 200 km, I know I can power the engine 50% with gasoline and 50% with battery power. This way, the internal combustion engine runs at a lower speed, making the trip more comfortable.