Select specific section in r markdown according to the user choice - R Shiny

[mosman2]

Assuming I have 2 r Rmarkdown files, When the user selects a certain input for example "1", I want to pull the first Rmarkdown file then, For each box in my dashboard, I want a specific section to be extracted from the selected Rmarkdown according to the box name. I would be so happy if you could assist me in this regard

library(shiny)
library(shinydashboard)
library(knitr)
ui <- 
dashboardPage(
dashboardHeader(title ='Virtual Excursion'), 

dashboardSidebar( sliderTextInput(
  inputId = "mySliderText", 
  label = "Story line", 
  grid = TRUE, 
  force_edges = TRUE,
  choices = c('1','2')
)
),
dashboardBody(
  fluidRow(
    column(9,  
           box(
             title = "Operations ", 
             closable = FALSE, 
             width = 9,
             status = "primary", 
             solidHeader = FALSE, 
             collapsible = TRUE,
             uiOutput("operations")
           )
    )
  ), 
  fluidRow(
    column(9, 
           box(
             title = "Challenges", 
             closable = FALSE, 
             width = 9,
             status = "primary", 
             solidHeader = FALSE, 
             collapsible = TRUE,
             uiOutput("challenges")
      )
     ) 
    )
   )
  )
   

  server <- function(input, output,session) {

  ChoseTheFile <- reactive({
  if (input$mySliderText == 1 )
  {
  # chose the first Rmarkdown file 
  else
  # chose the second Rmarkdown file  
  
  }
  }) 

  output$operations <- renderUI({
  #1  knit ChoseTheFile()
  #2  chose section 1 from ChoseTheFile()

  })

  output$challenges<- renderUI({
  #1  knit ChoseTheFile()
  #2  chose section 2 from ChoseTheFile()

  })

  }

  shinyApp(ui = ui, server = server)