Triggering the update from a buttom

updateCustomTextInputExample <- function(binding_step) {
  ui <- fluidPage(
    customTextInput(
      "caption",
      "Caption",
      "Data Summary",
      binding_step = binding_step
    ),
    actionButton("update", "Update text!", class = "btn-success"),
    textOutput("custom_text")
  )

  server <- function(input, output, session) {
    output$custom_text <- renderText(input$caption)
    observeEvent(input$update, {
      updateCustomTextInput("caption", value = "new text")
    })
  }
  shinyApp(ui, server)
}