Quick demo Shiny app with {bslib} using select inputs and checkbox

app.R

set.seed(123)
n <- 5
scheme <- paste("Scheme", 1:n)
mitigator <- paste("Mitigator", LETTERS[1:n])
combos <- tidyr::crossing(scheme, mitigator)
nrows <- nrow(combos)
dat <- combos |>
  dplyr::mutate(
    lo = runif(nrows),
    hi = pmin(lo + runif(nrows, 0.25, 0.5), 1),
    mid = (lo + hi) / 2,
    years = sample(20:30, nrows, replace = TRUE)
  )

ui <- bslib::page_sidebar(
  title = "Test facets",
  sidebar = bslib::sidebar(
    shiny::selectInput(
      inputId = "schemes",
      label = "Select schemes",
      choices = dat$scheme,
      selected = paste("Scheme", 1:3),
      multiple = TRUE
    ),
    shiny::selectInput(
      inputId = "mitigators",
      label = "Select mitigators",
      choices = dat$mitigator,
      selected = paste("Mitigator", LETTERS[1:3]),
      multiple = TRUE
    ),
    shiny::checkboxInput(
      inputId = "toggle_horizon",
      label = "Standardise by horizon length?",
      value = FALSE
    )
  ),
  bslib::card(
    bslib::card_header("Plot"),
    shiny::plotOutput("p"),
    full_screen = TRUE
  )
)

server <- function(input, output) {

  dat_selected <- reactive({

    shiny::validate(
      need(input$schemes, message = "Select at least one scheme."))

    shiny::validate(
      need(input$mitigators, message = "Select at least one mitigator.")
    )

    if (input$toggle_horizon) {
      dat <- dat |> dplyr::mutate(dplyr::across(c(lo, hi, mid), \(x) x / years))
    }

    dat |>
      dplyr::filter(
        scheme %in% input$schemes,
        mitigator %in% input$mitigators
      )

  })

  output$p <- shiny::renderPlot({
    dat_selected() |>
      ggplot2::ggplot() +
      ggplot2::geom_pointrange(
        ggplot2::aes(x = mid, y = scheme, xmin = lo, xmax = hi)
      ) +
      ggplot2::labs(x = "80% Confidence Interval") +
      ggplot2::facet_grid(~mitigator) +
      ggplot2::theme_bw(base_size = 20) +
      ggplot2::theme(axis.title.y = ggplot2::element_blank())
  })

}

shiny::shinyApp(ui, server)