Targeting/Adding traces in subplot

Hi - I'm trying to add/change traces in a graph with subplots. Below the example code.

It looks like each subplot becomes one trace (based on playing with the restyle section), but it is unclear to me how to add/remove traces. I changed the addTraces number at the end to 0-3 but it always adds it to the first subplot.

Any help would be appreciated.

data <- tibble(runmonth=c(1,1,1,1,4,4,4,4),variable=c('a','a','b','b','a','a','b','b'),x=c(1:8),y=c(8:1),keyname=paste0('k',c(1:8)))

p <- data %>% group_by(runmonth,variable) %>%
  do(
    p = highlight_key(., ~keyname,group='scattergroup') %>%
      plot_ly(showlegend = FALSE) %>%
      add_markers(
        x = ~x, y = ~y
      )
  ) %>%
  subplot(
    nrows = 2, margin = 0.01,
    shareY = TRUE, shareX = TRUE, titleY = FALSE
  ) %>% toWebGL() %>%
  highlight(
    on = "plotly_selected",
    off = c('plotly_relayout')
  )


ui <- function(id) {
  div(
    actionButton('go','go'),
    plotlyOutput("scattergr")
  )
}

server <- function(input,output,session) {
  
  output$scattergr <- renderPlotly({p})
  
  observeEvent(input$go,{
    plotlyProxy("scattergr", session) %>%
      plotlyProxyInvoke(
        "restyle",
        list(
          'marker.symbol' = list(c(rep('triangle-up',1),'circle'))
        ),
        list(0,1,2,3)
      ) %>%
      plotlyProxyInvoke(
        "addTraces",
        list(
          x = c(50,60),
          y = c(50,60),
          mode = "scatter"
        ),1
      ) %>%
      plotlyProxyInvoke(
        "moveTraces",
        -1,0
      )
  })
  

}

runApp(shinyApp(ui, server))

以提供的 Shiny 复现作为起点，重点关注 subplot 示例中对 restyle、addTraces 和 moveTraces 的 plotlyProxyInvoke 调用。确定 subplot 的 trace 索引行为预期是什么，以及结果应当是代码修正还是更清晰的文档；完成的标准是能够以可预测的方式定位所请求的 trace。