Well, it really depends on how Game Maker Studio stores CSV files, and/or how the CSV file you are wanting to read is setup.
CSV stands for "Comma Separated Value", meaning that every comma (
,) means a new value.
For example, here is what a simple CSV file could contain:
And with a CSV file formatted like this, we could parse it into a two dimensional array in Godot like this (untested):
var csv_array = 
var csv_file = File.new();
while not csv_file.eof_reached():
var csv_row = 
var csv_line = csv_file.get_line()
for element in csv_line.split(","):
# If you know the data will always be floats, use the following instead of the above.
# Then you can access the array like this:
# (Assuming there is something at that position)
print ("Example value at X=5 Y=2 : ", csv_array);
# To get the size of the data (assuming every row has the same size), you just do this:
var csv_size_column = csv_array.size();
var csv_size_row = csv_array.size();