Circuit details

From the LM2596S datasheet you can see that there is an internal voltage divider for the feedback voltage.

Increasing the output voltage is quite easy, you just need to add an external series resistance.

From the datashett the formula for the output voltage is

Rx means the additonal external resistor.

Mechanical modification

Only one trace needs to be cutted.

Remove a bit of the soldermask on both sides and solder a 0603 or 0805 resistor on top of that wire.