How to define names only for some option groups?

Question

I need a dropdown menu that would have certain groups of choices, with the first option being "Use all data". That choice makes up it's own option group, and this group doesn't need a name.
Unfortunately, selectInput() doesn't allow that. Either all option groups need to be names, or none of them can. I tried to manipulate the tags using htmltools and tagQuery(), but the individual optgroup-header tags cannot be accessed.

A reprex:

library(shiny)

grouped_options <- list(
  "Named category 1" =
    list(
      "list_choice1"
    ),
# this category shouldn't have a visible name
  "NONAME" = 
    list(
      "list_choice2",
      "list_choice3"
    ),
  "Named category 2" = 
    list(
      "list_choice5",
      "list_choice6"
    )
)

dropdown_element <- selectInput(inputId = "dd1",
                        label = "Dropdown menu with categorised options",
                        choices = grouped_options)

ui <- fluidPage(
  h1("Demo dropdown with categories"),
  dropdown_element,
  textOutput("sel_choice")
)

server <- function(input, output, session) {
  output$sel_choice <- renderText(input$dd1)
}

shinyApp(ui, server)

Answer 1

There is no need to use css or other utilities - just pass " " as a name:

" " = list(
    "list_choice2",
    "list_choice3"
)