How can I combine different density plots in a 3D plot?

Here one example:

julia> using Plots, KernelDensity

julia> data = [ randn(1000) for _ in 1:10 ]; # data for each coordinate

julia> densities = [ kde(dat).density for dat in data ]; # densities 

julia> density_matrix = hcat(densities...); # turn all into a matrix

julia> surface(density_matrix) # create surface

gives you:

image