I searched for a solution to this problem, and the best I can come up with was at https://moodle.org/mod/forum/discuss.php?d=176213
In there are several technical discussions about ways to change the TinyMCE editor, but the bottom line seems to be that people are just experimenting with it and not much progress has been made in the core code to allow users or admins to easily make the editor more customizable.
My particular need is to change the default size of the text and the font in all places where the editor appears.
Does ANYONE know an easy way to do this? Perhaps a few lines of code that can be inserted somewhere, with clear instructions where it has to go? I can do that, but I am not a PHP guru.
Any and all ideas are welcome. Thanks.