Feature request: Arrangement of guide legend box

[Yunuuuu]

Currently, ggplot2 only supports controlling the arrangement of keys within a single legend box via the nrow/ncol arguments in guide_legend(). However, there's no built-in way to control the arrangement of multiple legend boxes themselves (e.g., laying the legen box out in rows or columns when multiple legends are present).

This is the issue in stackoverflow
multiple legends arrangement, to create legends like this:

Would it be feasible to add support for arranging multiple legend boxes, through a new theme() option?

[teunbrand]

I can see why this is useful, but I imagine that if we introduce this then the next ask is going to be to do this for every position independently, so we'd have to introduce 5 new theme options for every position + a 6th one as a parent. The subsequent ask would then perhaps be how we could use arbitrary layouts (à la patchwork::plot_layout(design)).

The theme options as we have them currently are already pretty opaque as to what option pertains to what element of the guide(box) already. I'm not opposed to this, but perhaps we should rethink more thoroughly how users should interact with guide boxes/legends that doesn't perplex as much.