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Consider the user

That could easily be done by turning those styles into an enum and creating a std::array of the actual style strings.

Consider the user (part 1)

That could easily be done by turning those styles into an enum and creating a std::array of the actual style strings. For example, we might define the enum like this:

enum class Style{BasicStyle, LineStyle, DoubleLineStyle, InvisibleStyle};

Create the styles like this:

const std::array<ConsoleTable::TableStyle, 4> ConsoleTable::st = {{
    {"-", "|", {"+", "+", "+"}, {"+", "+", "+"}, {"+", "+", "+"}},
    {"━", "┃", {"┏", "┳", "┓"}, {"┣", "╋", "┫"}, {"┗", "┻", "┛"}},
    {"═", "║", {"╔", "╦", "╗"}, {"╠", "╬", "╣"}, {"╚", "╩", "╝"}},
    {" ", " ", {" ", " ", " "}, {" ", " ", " "}, {" ", " ", " "}},
}};

And now we can use them like this:

void ConsoleTable::setStyle(Style n) {
    style = static_cast<int>(n);
}

Naturally, the corresponding changes would need to be made wherever style was used.

Consider the user (part 2)

One way to do that:

bool ConsoleTable::update(const std::string &item, 
                          const std::string &col, 
                          const std::string &data) 
{
    auto row{std::find_if(rows.begin(), rows.end(), 
             [&item](auto &r){return r.front() == item;}) };
    auto hdrcol{std::find(headers.begin(), headers.end(), col)};
    if ((row != rows.end()) && (hdrcol != headers.end())) {
        (*row)[hdrcol - headers.begin()] = data;
        return true;
    }
    return false;
}

table.update("Australia", "Capitol", "Brisbane");

(Minor nit: it's spelled "capitol" in this context.)

table.update("Australia", "Capital", "Brisbane");