If you place cursor in the text of notes of an Impress presentation, Ctrl A will select all that note. Ctrl C will copy it; you can then Paste it into a Writer document. This must be done on a note by note basis. Apart from use of a macro (does one exist?), I know of no way to automate the process.
If the notes are already edited and formatted (within the limits of what Impress wiill allow) you can print them to a PDF file; this printout, unfortunately for your requirement, is of the Notes tab view - i.e., the slide and its accompanying notes. /File /Export as PDF seems to do the same. In a quick play with the settings I have found no way to export only the Notes.
In the internal file content.xml the note texts are distributed on a slide by slide basis, so it would not be an easy task to extract them other than with a macro.
https://ask.libreoffice.org/en/question/13188/how-to-export-impress-notes-only/offers a method of exporting to PDF and then removing the slides; however, a PDF file is not designed to be editable.
Apache OpenOffice 4.1.8 on Xubuntu 20.04.1 (mostly 64 bit version) and very infrequently on Win2K/XP