We need the schematics, to also put toggle switch for starting

Fitting a toggle switch for starting used to be a budget method of overcoming starter switch and other problems on older cars but will not work where the standard ignition key contains a transponder.

You haven't provided enough detail for a good answer but wiring a (spring return type) toggle switch to operate the starter motor is relatively easy and requires only a battery live and a wire to the starter solenoid or to the coil of the starter relay if you wish to use a relay.
Mostly these wires can be extended from the existing harness to the new switch.