thank you for your advice. But, I tried the way you proposed and didn't get the wished result. Trying to import again (in a new PAF file) the PAF-program offers the choices "Import Notes?" and "Report Import-problems in Notes?". I clicked both of them and imported with the same result as before: the ASSO-information was skipped.
The "hard-way" by copy and paste is excluded, because the gedcom-file comprises a complete church book with 43.000 persons.
What I hoped for was I could complement the new PAF-file by an additional data field "ASSO" and could command the import to direct the ASSO-information from the gedcom file to my field ASSO. Do you see any possibility of this kind?