Hi @salbol1 - In Designer you'll want to use the Interface tools, specifically the File Browse on the final Output Tool with an Action Tool for the path update.
The File Browse will specify the what to Save As.
The Action Tool will update the original Output file path that you used in the workflow in Designer.
You'll also want to view the Interface Designer to allow the user to choose the Save As selection in the app.
Just that setup alone will make the app run the workflow and generate the output as specified which would be the easiest/cleanest. There are also some Interactive Lessons via the Academy that can give you some walkthroughs that can help the setup as well.