我承认，这并不是完全普遍的。它要求您在服务器中放置一个向量，该向量具有UI中选项卡的名称。但是，你真的只需要两个按钮就可以让它工作（而不是每个选项卡两个按钮）。您只需要确保tab_id向量具有与UI相同顺序的正确名称。如果这是一个小规模的项目，其中选项卡和选项卡名称没有太大变化，那么您可能可以避免这样的事情。

library(shiny)
library(shinydashboard)
library(shinyjs)

### create general button here like: 
### write a function that looks at what (nth) tabItem we are, and creates a ###  uiOutput for a next_n button (I can do this myself I think) 

shinyApp(
  ui = 
    dashboardPage(
      dashboardHeader(title = "FLOW C.A.R.S."),
      dashboardSidebar(
        useShinyjs(),
        sidebarMenu(id = "tabs",
                    menuItem("Home", tabName = "Home", icon = icon("home")),
                    menuItem("My Page", tabName = "MyPage", icon =icon("download")),
                    menuItem("Do math", tabName = "Math", icon=icon("folder-open")),
                    menuItem("Results of something", tabName="Results", icon= 
                               icon("file-text-o")),
                    menuItem("Short Manual", tabName = "Manual", icon = icon("book"))
        )
      ),

      dashboardBody(
        hidden(actionButton(inputId ="Previous", label = icon("arrow-left"))),
        hidden(actionButton(inputId ="Next", label = icon("arrow-right")))
      )
    ),

  server = 
    shinyServer(function(input, output, session){

      tab_id <- c("MyPage", "Math", "Results", "Manual")

      observe({
        lapply(c("Next", "Previous"),
               toggle,
               condition = input[["tabs"]] != "Home")
      })

      Current <- reactiveValues(
        Tab = "Home"
      )

      observeEvent(
        input[["tabs"]],
        {
          Current$Tab <- input[["tabs"]]
        }
      )

      observeEvent(
        input[["Previous"]],
        {
          tab_id_position <- match(Current$Tab, tab_id) - 1
          if (tab_id_position == 0) tab_id_position <- length(tab_id)
          Current$Tab <- tab_id[tab_id_position]
          updateTabItems(session, "tabs", tab_id[tab_id_position]) 
        }
      )

      observeEvent(
        input[["Next"]],
        {
          tab_id_position <- match(Current$Tab, tab_id) + 1
          if (tab_id_position > length(tab_id)) tab_id_position <- 1
          Current$Tab <- tab_id[tab_id_position]
          updateTabItems(session, "tabs", tab_id[tab_id_position]) 
        }
      )
    })
)

正如我在评论中写道：最简单的肯定是重写代码并有一个数组：tabItemNames = c("Home", "MyPage",....)，然后相应地将选项卡命名为tabItem(tabName = tabItemNames[1],...)、tabItem(tabName = tabItemNames[2],...等。我不会称之为代码的冗余重复，...（另见本杰明的回答。
然而，我很欣赏JS的挑战，并给了它一个机会：您可以使用JS读取tabItemNames。这将满足不必在代码中硬编码它们的额外要求。

observe({
    runjs("
      function getAllElementsWithAttribute(attribute){
         var matchingElements = [];
         var allElements = document.getElementsByTagName('*');
         for (var i = 0, n = allElements.length; i < n; i++){
            if (allElements[i].getAttribute(attribute) !== null){
               matchingElements.push(allElements[i]);
            }
         }
         return matchingElements;
      };

      ahref = getAllElementsWithAttribute('data-toggle');
      var tabNames = [];
      var tabName = '';
      for (var nr = 0, n = ahref.length; nr < n; nr++){
         tabName = ahref[nr].hash.split('-')[2]
         if(tabName != 'Toggle navigation') tabNames.push(tabName)
      }
      Shiny.onInputChange('tabNames', tabNames);
      ")
  })

我假设你没有任何进一步的元素具有'data-toggle'属性。如果不能满足这一点，就必须在法典中加入更多的条件。
在下面一个运行的例子中，由上面的代码结合Benjamin提供的代码构建：

library(shiny)
library(shinydashboard)
library(shinyjs)

app <- shinyApp(
  ui = 
    dashboardPage(
      dashboardHeader(title = "FLOW C.A.R.S."),
      dashboardSidebar(
        useShinyjs(),
        sidebarMenu(id = "tabs",
                    menuItem("Home", tabName = "Home", icon = icon("home")),
                    menuItem("My Page", tabName = "MyPage", icon =icon("download")),
                    menuItem("Do math", tabName = "Math", icon=icon("folder-open")),
                    menuItem("Results of something", tabName="Results", icon= 
                               icon("file-text-o")),
                    menuItem("Short Manual", tabName = "Manual", icon = icon("book"))
        )
      ),

      dashboardBody(
        actionButton(inputId ="Previous", label = icon("arrow-left")),
        actionButton(inputId ="Next", label = icon("arrow-right"))
      )
    ),

  server = 
    shinyServer(function(input, output, session){
      global <- reactiveValues(tab_id = "")
      tab_id <- c("Home", "MyPage", "Math", "Results", "Manual")

      Current <- reactiveValues(
        Tab = "Home"
      )

      observeEvent(
        input[["tabs"]],
        {
          Current$Tab <- input[["tabs"]]
        }
      )

      observeEvent(
        input[["Previous"]],
        {
          tab_id_position <- match(Current$Tab, input$tabNames) - 1
          if (tab_id_position == 0) tab_id_position <- length(input$tabNames)
          Current$Tab <- input$tabNames[tab_id_position]
          updateTabItems(session, "tabs", input$tabNames[tab_id_position]) 
        }
      )

      observeEvent(
        input[["Next"]],
        {
          tab_id_position <- match(Current$Tab, input$tabNames) + 1
          if (tab_id_position > length(input$tabNames)) tab_id_position <- 1
          Current$Tab <- input$tabNames[tab_id_position]
          updateTabItems(session, "tabs", input$tabNames[tab_id_position]) 
        }
      )

      observe({
        runjs("
          function getAllElementsWithAttribute(attribute){
             var matchingElements = [];
             var allElements = document.getElementsByTagName('*');
             for (var i = 0, n = allElements.length; i < n; i++){
                if (allElements[i].getAttribute(attribute) !== null){
                   matchingElements.push(allElements[i]);
                }
             }
             return matchingElements;
          };

          ahref = getAllElementsWithAttribute('data-toggle');
          var tabNames = [];
          var tabName = '';
          for (var nr = 0, n = ahref.length; nr < n; nr++){
             tabName = ahref[nr].hash.split('-')[2]
             if(tabName != 'Toggle navigation') tabNames.push(tabName)
          }
          Shiny.onInputChange('tabNames', tabNames);
          ")
      })

    })
)

runApp(app, launch.browser = TRUE)

javascript函数从这里读取我使用的元素：Get elements by attribute when querySelectorAll is not available without using libraries?