Make acumalative graphics whit plotly Shiny R - r

Question

I must design a graph that accumulates variables as they are added in Shiny R using plotly.
For example, if I graph the variable x with respect to the date t with a select input, I add the variable and it is located on the right side of the variable x, indicating with a separator that it is the variable y and so with as many variables are selected.
This is my code:
library(shiny)
library(plotly)
library(dplyr)
set.seed(123)
df <- data.frame(x = seq.Date(as.Date("2000/1/1"), by = "month", length.out = 100),
cat = sample(c("m1","m2","m3"),100, replace = TRUE),
a = cumsum(rnorm(100)),
b = rnorm(100),
c = rnorm(100),
d = rnorm(100))
ui <- fluidPage(
selectInput("x","Variable",names(df)[-1],NULL,TRUE),
selectInput("y", "category", unique(df$cat), NULL, TRUE),
numericInput("ls","limite superior",NULL,-100,100),
numericInput("li","limite superior",NULL,-100,100),
plotlyOutput("plot1")
)
server <- function(input, output, session) {
output$plot1 <- renderPlotly({
req(input$y, input$x)
df <- df%>%
filter(cat %in% input$y)%>%
select(one_of("x",input$x))
estado <- ifelse(df[[2]]>input$ls,"red",
ifelse(df[[2]]<input$ls & df[[2]]>input$li,
"orange","green"))
df$estado <- estado
p <- plot_ly(df,
x = ~x,
y = ~df[[2]],
type = "scatter",
mode = "lines")
## Makers
p <- p %>%
add_trace(x = ~x,
y= df[[2]],
marker = list(color = ~estado, size = 20, symbol = "square"),
showlegend = FALSE)
## Lengends and labels
p <- p %>%
layout(legend = list(orientation = 'h'))%>%
layout(title = paste('Comportamiento de calidad de agua residual', input$estacion, sep=' '),
plot_bgcolor = "#e5ecf6",
xaxis = list(title = 'Fecha'),
yaxis = list(title = paste(input$x,"mg/l", sep=" ")))
print(p)
})
}
shinyApp(ui, server)
I need that when adding the variables a, b, c, d, the graph will be made just after the variable that was already there so that it looks something like this:

Answer 1

Use subplot and do function.
df %>%
group_by(category) %>%
do(p = plot_ly(...) %>% (plot_features...)) %>%
subplot(sharex= FALSE,sharey=TRUE, nrow=1, margin = 0.0001)
With plot feautures i mean all the deatils of the plot (markers, lines, colors, etc)