My code to concatenate several csv files is running very slow, how to optimize it? I have 200 csv files in a folder, with around 3000 lines each. I have this code to select the folder using a dialog, then it scans for files that match specific prefix and suffix. The final objective is to concatenate all files to a xlsx file, but the csv files do not have all the same number of columns. In that case, the columns should be kept as broad as possible (new columns should be added, with blank info when it does not exist for other files/lines). When I run the code below for 2...