How to combine legends from different ggplot after extracting via get_legend - r

Question

(EDIT: Removed original code and added reproducible example.)
I have two ggplot2 geom_tile plots.
Both have a legend.
The first one has one gradient scale.
The second one has two gradient scales.
Now I extract the legends from both plots via cowplot::get_legend(). The aim is to merge them to one legend and add it to the right of the composed final plot.
Then I try to combine them via: cowplot::plot_grid(legend1, legend2, ncol = 1, align = "v").
The problem is, that there is a large (EDIT: actually scaling) space between legend1 and legend2 (see figure below). I tried to remove margins of the legends via theme() when generating the initial geom_tile ggplots, but was not successful.
This there a way to completely "unwrap" the extracted legends and then stack them vertically afterwards into one ggplot figure?
Minimal example to showcase my problem:
m <- matrix(round(rnorm(200), 2), 10, 10)
colnames(m) <- paste("Col", 1:10)
rownames(m) <- paste("Row", 1:10)
df <- melt(m)
colnames(df) <- c("x", "y", "value")
df2 <- df
colnames(df2) <- c("x", "y", "value2")
library(ggnewscale)
ggplot1 <- ggplot(df, aes(x = x, y = y, fill = value)) +
geom_tile()
legend1 <- cowplot::get_legend(ggplot1)
ggplot2 <- ggplot() +
geom_tile(data = df2, aes(x = x, y = y, fill = value2)) +
ggnewscale::new_scale_fill() +
geom_tile(data = df, aes(x = x, y = y, fill = value))
legend2 <- cowplot::get_legend(ggplot2)
library(cowplot)
cowplot::plot_grid(legend1, legend2, ncol = 1, align = "v")
And here the result. The gap between the first scale and the second is too large -- what I learned just now, it that this large gap is being scaled according to the total size. So it seems to not be fixed:

Answer 1

When it comes to arranging plots it's always worthwhile to consider patchwork as an option. In your case you could use guides="collect" to arrange the legends without the need of extracting them first. However, at least for your example data one minor hack is necessary to show all legends, i.e. we have to add a space to the name of one of the value legends to prevent that they get merged.
library(ggplot2)
library(ggnewscale)
p1 <- ggplot(df, aes(x = x, y = y, fill = value)) +
geom_tile()
p2 <- ggplot() +
geom_tile(data = df2, aes(x = x, y = y, fill = value2)) +
ggnewscale::new_scale_fill() +
geom_tile(data = df, aes(x = x, y = y, fill = value)) +
scale_fill_continuous(name = "value ")
library(patchwork)
p1 / p2 + plot_layout(ncol = 1, guides = "collect")
DATA
set.seed(123)
m <- matrix(round(rnorm(100), 2), 10, 10)
colnames(m) <- paste("Col", 1:10)
rownames(m) <- paste("Row", 1:10)
df <- reshape2::melt(m)
colnames(df) <- c("x", "y", "value")
df2 <- df
colnames(df2) <- c("x", "y", "value2")