Using only certain pins on a sensor board
According to the schematic, if you only want to use the magnetometer, you need the following connections:


GND
+3.3V
GPIO_0 (SDA)
GPIO_1 (SCL)





You can use any one of the GND connections on the board. I typically use the closest to the power pin.



p.s.: since the other IC is also on the I2C bus, in case you want to use it in the future you do not have to make any additional connections.

p.p.s.: TL/DR, so, yes, you can just add 4 jumpers, you do not need all 26 connections..