Thank you for posting here, @Analec.

First, we'd like to know your answer to Fiat Lux - ASIA clarifying questions. This helps us address your concern and provide further information related to it.

We can utilize the Condense Data feature in your company file to help you to reduce the size of your file. Note: Condensing data in your account is irreversible.

1. Select File, then Utilities, and then Condense Data.
2. As illustrated below, choose the first choice. Please note that the system will inform you of the approximate file reduction.
   
3. Click Next and the message Working on your file now will show. When the optimization is finished, a window appears, informing you of the total file size reduction as well as the location of the backup file created before the optimization.

Afterward, let's reimport the data into your QuickBooks Online account.

Also, you can check about moving data from QuickBooks Desktop (QBDT) to QuickBooks Online (QBO): 

• Learn how to import your QuickBooks Desktop company file to QuickBooks Online.
• Learn how features and data move from QBDT to QBO.

Get back to us if you have any other questions while migrating data from QuickBooks Online to QuickBooks Desktop. I'm always here to help you sort things out.