How do I change the default font, so that when I create a new Rich Text note it is in the Font of my choice?
Select DEVONthink (or DEVONthink Pro) > Preferences > Editing. Then make your font choices for new documents. But if you are importing content from Web pages, you may need to change the default font used by your browser. And if the author of a Web page has specified a particular font, you may end up with that anyway.