[bs4Dash] how to remove leftUI element?

[beginnerR]

Below is the code from the bs4Dash demo. Only thing I have changed is disabling Sidebar. Interestingly, an element (pushmenu) is still remains and takes up space right next to the "title." Is there a way to remove this?

I have attempted to read bs4Dash document but couldn't find anything.
Thanks.
...

  library(bs4Dash)      
  ui <- dashboardPage(      
        dashboardHeader(title = "Title"),
        dashboardSidebar(disable=TRUE),
        dashboardBody(
        # Boxes need to be put in a row (or column)
              fluidRow(
                    box(plotOutput("plot1", height = 250)),
                    box(
                          title = "Controls",
                          sliderInput("slider", "Number of observations:", 1, 100, 50)
                    )
              )      
        )
  )

  server <- function(input, output) {
        set.seed(122)
        histdata <- rnorm(500)
        output$plot1 <- renderPlot({
        data <- histdata[seq_len(input$slider)]
        hist(data)
    })
  }

  shinyApp(ui, server)

...