It turned out to be Leelawadee UI for Windows 10 Professional.
For other OS versions, you can put the focus on the font dropdown, and up and down arrow, or press the first letter of the font, or press Home to go back to Automatic (the first dropdown option). Thereby, you can keep your eye on the Sample window to determine the default font. If you get on a font, then hit the Home key, and the Sample doesn’t change (even a little bit), that’s your default font. Please leave a comment if you find one!
