Modbus climate on/off switch

Is it possible to add a switch to a Modbus register or even to a home assistant switch entity?
Use case:
I have a PID controlled gas burner that works Automatically but sometimes I want to completely turn it off.
currently, I have a separate switch entity but it looks better in Lovelace if the climate entities can turn it on or off when changing the climate entity changing heat to off.
Template climate has this feature but it is used for bang-bang temperature control so it turns off if the current temp is above target temp, I want a steady on or off. (this control fan motors, safety gas valves, and the internal PID regulator.