Unfortunately I can't see Base X in UIFlow 1.0 either.
It looks like it got deleted from UI Flow several times:
https://community.m5stack.com/topic/3534/why-the-newest-uiflow-does-not-support-basex-anymore
I bought this (with the M5GO kit as well) to use with UIFlow for my child to control Lego. There was no warning when buying that this wasn't a supported system anymore.
Should I return it? Unfortunately not a great first experience with M5Stack.