In the general log [option 09] you can add comments to QSOs. These long comments cannot be <Entered> in the logging screen since there are no datafile fields set up for such inputs.
Use the File, Display log/data files menu.
The current log is hi-lighted.
Double-click it to open in your editor.
On the QSO line you want to edit, place the cursor at the end of the line. Use spaces to get to column 85 (see note) and type your comment. I tried 30 characters no problem. Log data at columns positions < 85 are used by the logger.
Re-save the log.
Go back to the logging screen and re-load the updated log file and continue logging.
I use EditPad since the column position of the cursor is displayed. If you want to use EditPad, copy the EditPad.exe to the GenLog32 folder and re-name NotePad.exe to something else.