Adding the No. of countries at the end of a regression table using estttab after using reghdfe

[Branon Xerxes]

I am using the reghdfe command for estimations at the subnational level (i.e. states and provinces) and would like to add a row at the bottom of the table which lists the number of countries in each column.
The country variable in the example below is CodeNum. While the number of countries in the example below does not change with columns, I envision future tables in the paper where the number of countries will intentionally change by column.
I tried N_hdfe as a scalar, but (a) that does not solve the problem since at least two columns do not have fixed effects, and (b) it returned a value of 1 for every column in the table when I tried initially (I am puzzled as to why that happened.)

    eststo clear
    reghdfe LnRegGDP denIn1850_25km_5k densqIn1850_25km_5k $coregeog if harmonized==1, noabsorb  vce(robust)
    qui estimates store model1
    reghdfe LnRegGDP denIn1850_25km_5k densqIn1850_25km_5k $coregeog $Xlist1  if harmonized==1, noabsorb  vce(robust)
    qui estimates store model2
    reghdfe LnRegGDP denIn1850_25km_5k densqIn1850_25km_5k $coregeog $Xlist1 if harmonized==1, absorb(contno)  vce(robust)
    qui estimates store model3
    reghdfe LnRegGDP denIn1850_25km_5k densqIn1850_25km_5k $coregeog $Xlist1  if harmonized==1, absorb(CodeNum) cluster(CodeNum)
    qui estimates store model4
    
    local indepvar "denIn1850_25km_5k densqIn1850_25km_5k"
    local tabletitle: var lab LnRegGDP 
* Prepare estimates for -estout-
    *Check estfe is installed.
    estfe model3 model4, labels(contno "Cont. FE" CodeNum "Country FE")
    return list
    
local addgeog "temp_mean  alt_mean rain_mean rug_mean temp_stdev rain_stdev inversedistcoast inversedistriver "

* Run estout/esttab
    esttab model* using "$results\baselinecityden_LnRegGDP_1850.tex",  replace ///
    indicate("Addl. Geog. Cntrl.=`addgeog'" `r(indicate_fe)') ///
    keep(`indepvar' $coregeog )  ///
    cells(b(star fmt(2)) se(par([ ]) fmt(2))) starlevels( * 0.10 ** 0.05 *** 0.010) nocons  ///
    label booktabs nonotes nomtitle collabels(none) ///
    title (`tabletitle') ///
    scalars( "N Obs." "r2_a Adj. R2" "r2_a_within  Adj. Wn. R2") sfmt(0 0 2 2) 
    
* Return stored estimates to their previous state
    estfe  model3 model4, restore