"What isn't working: there is no export button as explained on that page..."
The demo in the link you provided works well in r2019a and r2016b (those are the releases I tested).
Hover your mouse over the axes and a row of icons should appear in the upper, right corner, one of which is the export button.
If that's not working in r2019a, make sure toolbar visibility is on.
axh = gca();
axh.Toolbar.Visible = 'on';
From the menu bar, select File > Export Setup.
Turn on the menu bar if it's not visible.
fh = gcf();
fh.MenuBar = 'Figure';
Alternatively, do it programmatically.
Follow the steps in the link you proivded to do it without the export button.
"1) Those 2 lines of code did not work for me..."
Again, what didn't work? I'm sure it didn't result in an error.