I'm having the same issue and the only solution I could find is to change the settings in Windows and use the US format (comma instead of a period and vice-versa).
Does anyone have a different solution?
I really doubt there is anyway to do this. Best to create an Idea for this so the Devs see it.
Tableau (actually Jet) will pick this setting up from Windows. If you want to override it, you need to create a schema.ini file. See documentation at Schema.ini File (Text File Driver). You need to set the DecimalSymbol property.
Thanks Dan, that's good to know.