Redirecting button click to a navbar tab nested inside another navbar tab in R shiny

I have a web app made with R Shiny. It has a navbar and three tabs in it. Let us call them parent tabs. The third parent tab has a navbar in it with four children tabs and my first parent tab has a button. Now, when I click the button, it should take me to the second child tab of the third parent tab. I tried to do this using updateTabsetPanel and updateNavbarPage however, I couldn't do it. Are there any other ways to make this work? This is the sample UI code

library(shiny)


ui <- shinyUI(fluidPage(
  titlePanel("My Web App"),
  
  navbarPage(
    "My App",
    id = "first_nav",
    tabPanel(title = "Tab 1",
             value = "tab_1",
             actionButton("btn_tab3", "Go to tab 3.2")
    ),
    tabPanel(title = "Tab 2",
             value = "tab_2",
             h2("This is Tab 2")
    ),
    tabPanel(title = "Tab 3",
             value = "tab_3",
             h2("This is Tab 3"),
             fluidRow(),
             navbarPage(
               title = "third tab navbar",
               id = "second_nav",
               tabPanel(title = "tab 3.1",value = "tab_3_1",h2("This is 3.1")),
               tabPanel(title = "tab 3.2",value = "tab_3_2",h2("This is 3.2")),
               tabPanel(title = "tab 3.3",value = "tab_3_3",h2("This is 3.3")),
               tabPanel(title = "tab 3.4",value = "tab_3_4",h2("This is 3.4")),
             ),

    )
  )
))

server <- shinyServer(function(input, output, session) {
  
  observeEvent(input$btn_tab3, {
    #code for switching tabs on button click
  })
  
})

shinyApp(ui = ui, server = server)

First, correct the typos in your code. Next, add a call to library(shiny) at the head of your program and write a server function. Then call shinyApp.

Next, wrap your tabPanels in calls to tabsetPanel and remove the nested navbarPage on the third tab. I didn't investigate whether you can nest navbarPages, but even if you can, you need to provide values to the parameters it expects. I've replaced it with a couple of calls to fluidRow.

Finally, use observeEvent to detect your button click and respond appropriately.

Here is a minimal reproducible example. You should be able to simply cut and paste the code into your IDE and run it to see the results. Ideally, your question would have allowed us to do the same.

library(shiny)

ui <- fluidPage(
  ui <- shinyUI(fluidPage(
    titlePanel("My Web App"),
    
    navbarPage(
      "My App",
      id = "first_nav",
      tabsetPanel(
        id = "tabsetPanel1",
      tabPanel(title = "Tab 1",
               value = "tab_1",
               actionButton("btn_tab3", "Go to tab 3.2")
      ),
      tabPanel(title = "Tab 2",
               value = "tab_2",
               h2("This is Tab 2")
      ),
      tabPanel(title = "Tab 3",
               value = "tab_3",
               h2("This is Tab 3"),
               fluidRow(),
               fluidRow(
                 "third tab navbar",
               ),
               fluidRow(
                 tabsetPanel(
                   id = "tabsetPanel2",
                 tabPanel(title = "tab 3.1",value = "tab_3_1",h2("This is 3.1")),
                 tabPanel(title = "tab 3.2",value = "tab_3_2",h2("This is 3.2")),
                 tabPanel(title = "tab 3.3",value = "tab_3_3",h2("This is 3.3")),
                 tabPanel(title = "tab 3.4",value = "tab_3_4",h2("This is 3.4"))
                 ),
               )
            ),
        )
      )
    )
  )
)

server <- function(input, output, session) {
  observeEvent(input$btn_tab3, {
    updateTabsetPanel(session, "tabsetPanel1", "tab_3")
    updateTabsetPanel(session, "tabsetPanel2", "tab_3_2")
  })
}

shinyApp(ui = ui, server = server)