Positioning Nested Categories in Gmisc Flowchart

Question

I'm using the Gmisc package in R to design a flowchart based on nested categorical data, similar to the gtcars example. My main challenge: I can't correctly stack many subcategories (akin to mfr in gtcars) under their respective ctry_origin categories. Despite referencing the package's vignette, I'm still facing positioning issues. Can anyone offer advice on this layout?

Data:

library(Gmisc)
library(gt)
gtcars %>% select(ctry_origin, mfr) %>% filter(ctry_origin %in% c("Germany", "Italy", "Japan")) %>% group_by(ctry_origin, mfr) %>%
  summarise(count = n()) %>%
  arrange(ctry_origin, desc(count))

How I would like my flowchart to look like using mermaid() from the DiagrammeR package.

# Stackoverlflow
mermaid("
graph TB
A[Cars]-->B[Germany 16]
A[Cars]-->C[Italy 15]
A[Cars]-->D[Japan 2]

B-->1[Audi 5]
1---2[BMW 5]
2---3[Porsche 4]
3---4[Mercedes-Benz 2]
C---5[Ferrari 9]
5---6[Lamborghini 3]
6---7[Maserati 3]
D---8[Acura 1]
8---9[Nissan 1]
")

My attempt:

### Flow chart with my data
# Create the boxes
cars <- boxGrob(glue("Cars",
                                "n = {n}",
                                n = txtInt(33),
                                .sep = "\n"),
                           x = 0.5,
                           y = 0.9)
cars.ger <- boxGrob(glue("Germany",
                                    "n = {n}",
                                    n = txtInt(16),
                                    .sep = "\n"),
                               x = 0.2,
                               y = 0.5)
cars.ita <- boxGrob(glue("Italy",
                                   "n = {incl}",
                                   incl = txtInt(15),
                                   .sep = "\n"),
                              x = 0.5,
                              y = 0.5)
cars.jap <- boxGrob(glue("Japan",
                                   "n = {recr}",
                                   recr = txtInt(2),
                                   .sep = "\n"),
                              x = 0.8,
                              y = 0.5)
cars.audi <- boxGrob(glue("Audi",
                         "n = {n}",
                         n = txtInt(5),
                         .sep = "\n"),
                    x = 0.2,
                    y = 0.7)
cars.bmw <- boxGrob(glue("BMW",
                         "n = {incl}",
                         incl = txtInt(5),
                         .sep = "\n"),
                    x = 0.2,
                    y = 0.7)
cars.porsche <- boxGrob(glue("Porsche",
                         "n = {recr}",
                         recr = txtInt(4),
                         .sep = "\n"),
                    x = 0.2,
                    y = 0.7)
cars.mercedes <- boxGrob(glue("Mercedes",
                         "n = {n}",
                         n = txtInt(2),
                         .sep = "\n"),
                    x = 0.2,
                    y = 0.7)
cars.ferrari <- boxGrob(glue("Ferrari",
                         "n = {incl}",
                         incl = txtInt(9),
                         .sep = "\n"),
                    x = 0.5,
                    y = 0.7)
cars.lamborghini <- boxGrob(glue("Lamborghini",
                         "n = {recr}",
                         recr = txtInt(3),
                         .sep = "\n"),
                    x = 0.5,
                    y = 0.7)
cars.maserati <- boxGrob(glue("Maserati",
                         "n = {n}",
                         n = txtInt(3),
                         .sep = "\n"),
                    x = 0.5,
                    y = 0.7)
cars.acura <- boxGrob(glue("Acura",
                         "n = {incl}",
                         incl = txtInt(1),
                         .sep = "\n"),
                    x = 0.7,
                    y = 0.7)
cars.nissan <- boxGrob(glue("Nissan",
                         "n = {recr}",
                         recr = txtInt(1),
                         .sep = "\n"),
                    x = 0.7,
                    y = 0.)
grid.newpage()
cars
cars.ger
cars.ita
cars.jap

# Connect main boxes with arrows
connectGrob(cars, cars.ger, "N")
connectGrob(cars, cars.ita, "v")
connectGrob(cars, cars.jap, "N")

spread_boxes <- spreadVertical(cars.ger, cars.audi,
                               cars.bmw,.type = "between")
for (b in spread_boxes) {
  print(b)
}