How to adjust the output table generated in a shiny code

In the datatable options, it's scrollX and not scrollx, change that and you get your desired output.

output$table <- renderDataTable({
    datatable (
      data_subset(),
      options = list(
        columnDefs = list(list(className = 'dt-center', targets = "_all")),
        paging = TRUE, 
        searching = FALSE, 
        pageLength =  10,
        dom = 'tip',
        scrollX = TRUE
      ),
      rownames = FALSE
    ) 
  })