R shiny - checkboxes and action button combination issue

I have 2 checkboxes and 1 action button. When clicking on either of the checkboxes, a graph should output BUT only after clicking on the action button. The code I have bellow does this well already. My issue here is that once the action button has been clicked and the graph generated, unclicking the checkbox removes the graph. Similarly, clicking again generates a new graph without clicking on the action button. I would like for the graph to stay on the screen for as long as I dont click on the action button again. I imagine this has to do with "isolating" the checkboxes but Im not too sure how to do so.

As a side note, imagine there was a third function generating a plot in my server when clicking on the action button (regardless of the checkboxes). Is there a way to code my "showmodal, removemodal" such that the pop up stays while all functions are running (instead of only during the first function)?

Here is my code

library(shiny)

#Function 1
X <- function(a,b,c){
    plot(c(a,b),c(b,c))
}

#Function 2
Y <- function(d,e,f){
    plot(c(d,e),c(e,f))
}

ui <- fluidPage(
    
    titlePanel("title"),
    
    sidebarLayout(
        sidebarPanel(
            checkboxInput("EF", "Efficient Frontier"),
            checkboxInput("MonteCarlo", "Monte Carlo Simulation"),
            actionButton("Go", "Go", style="color: #fff; background-color: #337ab7; border-color: #2e6da4; margin: auto")
        ),
        
        mainPanel(
            fluidRow(
                align = "center",
                conditionalPanel(condition = "input.EF == true", plotOutput("GraphEF")),
                conditionalPanel(condition = "input.MonteCarlo == true", plotOutput("GraphMC"))
            )
        )
    )
)

server <- function(input, output) {
    
    OPw <- reactiveValues()
    output$Graphw <- renderPlot({ 
        OPw$PC}, height = 400, width = 400)
    
    observeEvent(input$Go, {
        showModal(modalDialog("Loading... Please Wait", footer=NULL)) 
    
        output$GraphEF <- renderPlot({ #Efficient Frontier
            if(input$EF){
                X(5,10,15)
            }
        }, height = 550, width = 700)
        
        output$GraphMC <- renderPlot({ #Monte Carlo Simulation
            if(input$MonteCarlo){
                Y(5,10,15)
            }
        },height = 550, width = 700)
        
        removeModal() #Removes Loading Pop-up Message
        
        
    })
}

shinyApp(ui = ui, server = server)

Thanks a lot for your help!