Hello RhoiceW -  The salient feature of what you had to say is the piece about the replacement of the existing data.  This lets me know that an append does not take place.  

I'm going to follow 4Gal's advice about migrating and merging data on a PC version of QB.  I hope to be able to gather the previous data kept on QBO prior to 2023 and bring it into my desktop file which only has 2023 data.  After this is done, I can then upload the completed file to QBO which will replace the current online file. Many thanks for your reply and thoughtful response.