Add and change points

using Makie
 using LinearAlgebra

 img = rand(100, 100)
 scene = Scene(scale_plot = false, resolution = (500, 500))
 heatmap!(scene, img)
 clicks = Node(Point2f0[(0, 0)])
 blues = Node(Point2f0[])
 on(scene.events.mousebuttons) do buttons
     if ispressed(scene, Mouse.left)
         pos = to_world(scene, Point2f0(scene.events.mouseposition[]))
         found = -1
         c = clicks[]
         for i in 1:length(c)
            if norm(pos - c[i]) < 1
                found = i
            end
         end
         if found >= 1
             blues[] = push!(blues[], pos)
             deleteat!(clicks[], found)
         else
             push!(clicks[], pos)
         end
         clicks[] = clicks[]
    end
    return
 end
 t = Theme(markersize = 10, raw = true)
 scatter!(scene, t, clicks, color = :red, marker = '+')
 red_clicks = scene[end]
 scatter!(scene, t, blues, color = :blue, marker = 'o')
 center!(scene)
 RecordEvents(scene, "output")