Legend are grob objects. You can construct a single legend by Legend() and arrange multiple legends by packLegend(). Later the legend can be put at any place in the plot by draw(lgd, x, y, ...).

See https://jokergoo.github.io/ComplexHeatmap-reference/book/legends.html

Note if you do this way, the space for the legends is not calculated anymore, which means, you need to manually arrange the white space for legends.

m = matrix(rnorm(100), 10)
Heatmap(m)

lgd = Legend(title = "foo", at = letters[1:4], legend_gp = gpar(fill = 1:4))

draw(lgd, x = unit(0.5, "npc"), y = unit(0.5, "npc"))

How to get the automatically generated legend objects by Heatmap() and HeatmapAnnotation()? so they can be included in packLegend() along with those legend object specifically defined by Legend().

Here is my code, where lgd1 and lgd2 are two objects defined by Legend(), named as WK24.PC and cytokines.

TD2TI and Hgb.RESP are two auto-generated legends for row annotation. log10 BL/mean is the auto-generated legend for the heatmap body.

I'd like to move all the legends to a coordinate. But if I add x = unit(0.5, "npc"), y = unit(0.5, "npc"), it doesn't work for draw,Heatmap-method

cRe=Heatmap(...)
draw(cRe, annotation_legend_list = list(lgd1,lgd2), merge_legend = TRUE)

Then you need to manually construct all legends. It will be something like:

lgd = packLegend(
    Legend(title = "TD2TI", at = c("FALSE", "TRUE"), legend_gp = gpar(fill = c("red", "greem"))),
   ... # same for other discrete legend,
    Legend(title = "log10\nBL/mean", col_fun = your_col_fun, ...),
   ... # other legends
)

and remember to turn off all the default legends:

Heatmap(..., top_annotation = HeatmapAnnotation(..., show_legend = FALSE), show_heatmap_legend = FALSE)
draw(lgd, x, y, ...)