There is no direct way to convert QuickBooks Online to QuickBooks Desktop. but here is a way.
One workaround is to use the Intuit Intercompany Transfer feature. This feature allows you to export data from QuickBooks Online and import it into QuickBooks Desktop. To use the Intuit Intercompany Transfer feature, you will need to:
Open QuickBooks Online and go to Company > Import Data > Intercompany Transfer.
Select the data that you want to export and click Export.
Open QuickBooks Desktop and go to Company > Import Data > Intercompany Transfer.
Select the exported file and click Import.
The Intuit Intercompany Transfer feature will import the following data from QuickBooks Online to QuickBooks Desktop: