Adding storage to a Chuwi Hi12

I have a Chuwi Hi12 dual boot tablet with Windows 10 and Android 5.1. The tablet details are CW1520 64bit Hi12 Q64G45170404873.

I would like to add some fully addressable storage and was wondering what was the best solution in terms of speed and accessibility?

Ideally, the additional storage would be seen as fully integrated system storage like an additional hard drive or SSD would be on a PC. Any suggestions gratefully received.

Memory in tablet are soldered to main board, it’s can’t be extended only replaced with another EMMC. You can just use sd card or external ssd for additional storage.

Thank you for replying.

I don’t understand how you can format a single SD card to be formatted for use by both Windows and Android. Won’t the file systems conflict?

Windows and Android both supports exFAT.