Thanks for reporting this issue, Illustrator team really appreciate this.
Unfortunately we are unable to reproduce this issue in house, Kindly help Illustrator Team to nail this issue down further:
Kindly provide the exact preferences you are using and the data from below mentioned location .
Mac:- /Users//Library/Preferences/Adobe Illustrator 2X Settings
Win:-C:\Users\\AppData\Roaming\Adobe\Adobe Illustrator 2X Settings
Share the above information with us at ShareWithAI@adobe.com in a Zip file. Please mention the title of this issue as the subject of the mail.
Thanks and Regards
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I have this problem on both Mac & Windows Illustrator v23 2019, preferences will not save as every time I reopen the application preferences are reset to default....very annoying.