Is it possible to control DC-DC boost convertor by N-ch MOSFET @ Vin-?
If the MT3608 module's ground ( = IN- = OUT-, these pins are shorted on the module) is kept separate from the rest of the circuit then: yes you can.

The schematic should look like this:







simulate this circuit &ndash; Schematic created using CircuitLab

I have added a current limiting resistor R1, because the 12 V LED COB modules I have seen all need a constant current, not a constant voltage. Maybe your LEDs are different. I do not know, but I just mention this to warn you of potential issues that occur if you apply 12 V directly to LED modules which actually need a current instead of a voltage.