如果没有数据的例子，很难测试这一点，但是你可以尝试将盒子 Package 在一个容器中，并将display: flex应用于该容器。
代码应该是这样的

library(shiny)
ui <- fluidPage(
  tags$head(
    tags$style(
        "
        .flex-container {
          display: flex;
        }
        <!--  Because I do now have actual code and figures I've added border around the box (this may not be needed in your case) only flex-container -->
        .shiny-box {
          border: 1px solid black;
          padding: 20px;
          margin: 5px;
          flex: 1;
        }
"
    )
  ),
  
  div(class = "flex-container",
      div(class = "shiny-box", "UAE customs efficiency."),
      div(class = "shiny-box", "Clear exports. some text some more text some more text gor height purposes ............"),
      div(class = "shiny-box", "Clear imports.")
  )
)

server <- function(input, output) {
  
}

shinyApp(ui, server)

输出