Dear respected Princewill Sunday,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, using Visio Data Visualizer add-in in Excel and creating a flow chart in Excel, generally, the diagram is saved as a Visio file in your OneDrive location.
In Excel click on Edit button, it will create a Visio file into your OneDrive> Visio Data Visualizer folder location.
The you may open in Visio desktop client app and it automatically export from Excel to Visio.
Appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Waqas Muhammad