@Le18BR I built a workflow that would remove leading and closing quotation marks (if a ‘legitimate’ double quotation is in the first or last column the workflow will have to be modified).
The idea ist to read the CSV as one string in one column. Clean the columns according to several rules, export it again as CSV and then read the thing back into KNIME as a ‘clean’ CSV. The R Readr package should be able to handle double escapes but it did not work immediately.
Again my recommendation stands: use other file formats like Parquet, ARFF or SQLite to transfer data 
The result should be OK. If additional strange things appear they might also be removed from the single imported line:
kn_forum_44692_csv_file_comma.knwf (81.6 KB)