In coppercube's documentation there is a Javascript reference glossary: https://www.ambiera.com/coppercube/doc/index.html
But basically, once you created the txt file using 5v3n plugin you can use 'ccbReadFileContent(filename)' to load the file and
'ccbSetCopperCubeVariable(varname, value)' to send them into a var. something like this:
ccbSetCopperCubeVariable("nodes",ccbReadFileContent("Lvl1.txt"));
You may need to first create the coppercube variable in the engine doing a 'When scene load' -> 'set or change a variable'
(IDK how is in english, i have coppercube in Spanish).
Is one of the very first thing the game does. The .ccb is inside the folder in case you wanna check it out. Sorry i didn't documented it.