My dog needs to be in car for short periods and she sets off alarm, friend told me to leave car unlocked but not ideal. Checked manual to see if I can disable alarm occasionally but can't find this.

If equipped, the car has a button to disable the motion sensor. Check the B pilar on the drivers side. It is a button between the seat and the pillar between front and rear seats. it usually is located there very low. But check your manual as this may vary, and even if you don;t have the option it must be specified in it.