How to great variables

[wint0178]

I'm running a MyController v 2.0 server on Rasp Pi v4. The server is setup on a DDNS so that I can send data from gateways and notes in remote locations back to the server and gain access world wide. I have had some success using the available MySensors example sketches in Adruino libraries in getting the BME680, for example, connected and transmitting data, but I am trying to add in other Adafruit boards and am getting cought up on defining the variables. As an example, I noticed that the BME680 has a gas sensor along with temp, press, and humidity. So, using the available example, I tried to create a variable for the gas value AND for the two values that are available on the CCS811 board as follows:

//create mysensors varibles, send as V_custom not as a JSON 
MyMessage temperatureMSG(TEMP_CHILD_ID, V_TEMP);
MyMessage humidityMSG(HUM_CHILD_ID, V_HUM);
MyMessage pressureMSG(BARO_CHILD_ID, V_PRESSURE);
MyMessage gasMSG(GAS_CHILD_ID, V_GAS);
MyMessage coMSG(CO_CHILD_ID, V_CO);
MyMessage tvocMSG(TVOC_CHILD_ID, V_TVOC);

But, I get the error (FYI, I cut most of the top of the compiling log believing it is not helpful here):

Using library MySensors at version 2.3.2 in folder: /Users/bjw58994/Documents/Arduino/libraries/MySensors 
Using library SPI at version 1.0 in folder: /Users/bjw58994/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/SPI 
Using library ESP8266WiFi at version 1.0 in folder: /Users/bjw58994/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/ESP8266WiFi 
Using library EEPROM at version 1.0 in folder: /Users/bjw58994/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/EEPROM 
Using library Wire at version 1.0 in folder: /Users/bjw58994/Library/Arduino15/packages/esp8266/hardware/esp8266/2.7.4/libraries/Wire 
Using library Adafruit Unified Sensor at version 1.1.14 in folder: /Users/bjw58994/Documents/Arduino/libraries/Adafruit_Unified_Sensor 
Using library Adafruit BME680 Library at version 2.0.4 in folder: /Users/bjw58994/Documents/Arduino/libraries/Adafruit_BME680_Library 
Using library Adafruit BusIO at version 1.15.0 in folder: /Users/bjw58994/Documents/Arduino/libraries/Adafruit_BusIO 
Using library Adafruit CCS811 Library at version 1.1.3 in folder: /Users/bjw58994/Documents/Arduino/libraries/Adafruit_CCS811_Library 
Using library RadioHead at version 1.122.1 in folder: /Users/bjw58994/Documents/Arduino/libraries/RadioHead 
exit status 1

Compilation error: 'GAS_CHILD_ID' was not declared in this scope

Ultimately, I don't understand how to define or pick a variable, I thought it was user defined, but this makes me think perhaps they are already defined in a library somewhere. Any help in directing me to either the correct structure/sytax of the variables or the location they are defined would be great. Thanks!