How to put a single marker on a heatmap

[icweaver]

I think your single points just need to be wrapped in a vector:

using CairoMakie

fig = Figure()
ax = Axis(fig[1, 1])

heatmap!(ax, rand(4, 4))
scatter!(ax, [2.5], [2.5]; marker='😃', markersize=100)

# Can also use a Point
scatter!(ax, Point(3.5, 1.5); marker='😃', markersize=100)

fig

Edit: added an example using Point