File selection window opens behind R main window

Question

I saw this question has been asked before but not answered. When using tcltk::tk_choose.files() the first time during an R session it opens behind the R main window. All further times it opens in front of the main window (as it should!). Is there a way to have it always in the very front? Ultimately I would like to use it via shiny as below. So it should also be in front of the shiny window.

library(shiny)

ui <- fluidPage(
    actionButton("do", "Open window")
)

server <- function(input, output, session) {
    observeEvent(input$do, {
        tcltk::tk_choose.files()
    })
}

shinyApp(ui, server)

I am aware of base::file.choose() and utils::choose.files(). However, the first does not allow to select multiple files at once and the second does not allow to copy/paste paths for quicker navigation which drives me crazy,..