How to set max length for editor TinyMCE?

When you initialize TinyMCE, you have possibility to add a setup with a function that has an eventlistener. Inside this function, you determine the max length; in your case 10, then you take the length of the text (targetted with .getContent())... and compare both. If content length is too long, you send an error message, disable the save button, or whatever you want.