I'm looking to create repeatable metaboxes with 3 fields (name, website and description), very similar to this tutorial https://gist.github.com/helen/1593065 which serves as the foundation for my code. However, I don't fully understand how to introduce a wysiwyg editor for the description (ideally, in place of the select dropdown within the tutorial). I'm just now getting the slightest bit comfortable with php so any comments with a solution would be most welcome.
Handling the repeating editor is kind of tricky in WordPress as it requires custom JavaScript code to work on the DOM. WordPress doesn't support repeating fields by default. Besides, the code you're reference to is 7 years old.
I'd suggest using Meta Box plugin, which has a Meta Box Group. It helps you build repeatable groups easily with some PHP code.
If you don't want the repeating group of fields, you can still make a single field repeatable. This feature is called clone and is supported in the free version of the plugin.