How to draw boxes around subfigures
If you want to show that several elements in a Figure belong together, you can do this by placing them all in a container. The trick is to use a nested GridLayout for each group of objects and place a Box at the same position as this GridLayout. Then the alignmode = Outside(some_padding) ensures that objects with protrusions sticking out, like Axis, are fully contained within the enclosing boxes.
julia
using CairoMakie
f = Figure()
g1 = GridLayout(f[1, 1], alignmode = Outside(15))
g2 = GridLayout(f[1, 2], alignmode = Outside(15))
box1 = Box(f[1, 1], cornerradius = 10, color = (:tomato, 0.5), strokecolor = :transparent)
box2 = Box(f[1, 2], cornerradius = 10, color = (:teal, 0.5), strokecolor = :transparent)
# move the boxes back so the Axis background polys are in front of them
Makie.translate!(box1.blockscene, 0, 0, -100)
Makie.translate!(box2.blockscene, 0, 0, -100)
Axis(g1[1, 1], backgroundcolor = :white)
Axis(g1[2, 1], backgroundcolor = :white)
Axis(g2[1, 1], backgroundcolor = :white)
Axis(g2[1, 2], backgroundcolor = :white)
Axis(g2[2, 1:2], backgroundcolor = :white)
Label(f[0, :], "Two boxes indicate groups of axes that belong together")
f