There is no option as such in Tableau to disable auto grouping.
But there is work around.
two ways you could achieve this
1. Create index() and drag this as your first row item. Now you shouldn’t be seeing any grouping. To hide this field at index() drop down uncheck “show header”
2. Drag “Number of Records” measure as first row. Do a quick table calculation as — running total, sum, table down. This would give similar data like index(). And data is not grouped anymore. To hide this field uncheck “show header”