Add whitespace/gap between column title and first row of the heatmap body

[kloot]

Ho can I add a little whitespace/gap between the column title 'box' (orange, green in the pic below) and the first row of the heatmap body?

I have experimented with ht(opt).
ht_opt("TITLE_PADDING" = unit(c(2, 1), "mm") allows me to adjust the height of the box and the vertical position of the label ('classical monoc') in the box, but ht_opt("COLUMN_ANNO_PADDING") seems to have no effect at all.

The relevant code to generate the heatmap in the (partial) screenshot:

ht_opt(RESET = TRUE)
Heatmap(data, name = "mat",
        row_order = rownames(data),
        row_names_gp = gpar(fontsize = 9),
        
        column_split = split_order %>% select(curated_labels),
        column_order = split_order %>% row.names(),
        column_gap = unit(c(1, 0.5), "mm"),
        show_column_names = FALSE,
        column_title_gp = gpar(fill = c("orange", "forestgreen", "#0033cc"),
                               fontsize = 7),
        border=FALSE,
        ht_opt("HEATMAP_LEGEND_PADDING" = unit(c(5, 5), "mm"),
               "TITLE_PADDING"          = unit(c(2, 1), "mm"), # bottom, top
               "COLUMN_ANNO_PADDING"    = unit(c(30, 10), "mm"),
               "DIMNAME_PADDING"        = unit(1, "mm")        # distance row/column annotation to heatmap  
               )
        )

Many thanks in advance!