For example, suppose I want the simple line demo in the Makie docs rendered into a 5000x3000 PNG:
using Makie
x = range(0, stop = 2pi, length = 40)
f(x) = sin.(x)
y = f(x)
scene = lines(x, y, color = :blue; resolution=(5000,3000));
Makie.save("out.png", scene)
The resulting PNG is cropped to 3844x2124 and shows just the lower left of the full scene. (And those dimensions are a bit weird considering I have a standard 4K screen at 3840x2180.)