4:54 AM
You asked what is the use what chip select signal CS0 and CS1. This is what I answered in the answer I referred. You need to wiki and google SPI to understand everything. But for my dual ST7789 LCD project, it is something like this. I am connecting two LCD modules to the same SPI0 bus, each module as the same SCLK, MOSI, MISO wires connected. The only difference is that module A CS pin is connected to SPI CS0 pin, and Module B's CS pin is connected to SPI CS1 pin.
Now if I set CS0 Low, and CS1 High, then Module A will be selected, and will talk to Rpi through SPI CLK, MOSI, MISO wires. At the same time, Module B is NOT selected, and will not respond to SPI signals.
Now the catch is this. For your 7 pin module, the LCD's CS wire is CONNECTED TO GROUND, therefore ALWAYS SELECTED, no matter Rpi's CS0, CS1 are High or Low, LCD does not care, always respond. So what I suggested to the OP of that question is suggesting him to extract the LCD's CS wire, DO NOT CONNECT TO GROUND, but connect to Rpi SPI CS1, then this modified LCD will be selected if Rpi SPI CS1 is low.
I have been trying to explain this to a coople of other user asking why they can not use two LCDs. But they don't try to understand what I am talking about, and gave up, ... :(