You can usually put the finish of one coil to the beginning of the next coil and you will have two pickups in series. Providing they are both wound in the same direction and have the same magnet polarity they will have proper phasing. If you ground the beginning from both coils and make both finishes a hot connection, the two pickups will be in parallel. When the two coils are connected in series you can add a switch to the middle to split the two pickups making only one operative. The older Fender Duo-Sonics from the late 50’s had two pickups hooked up in series for a unique tone and blend of pickups. I have an old ’57 Duo-Sonic guitar and love the pickup combinations and tone possibilities.