In this tutorial – published Oct. 5, 2018 – Rich Tape gives a great overview of block editor terminology along with example code for adding a custom panel to the block editor sidebar.
- Simplifying terminology used in block editor development
- Registering and rendering a custom block setting panel
- Whitelisting the panel for specific block types
Rich does a great job breaking down some of the vernacular the Gutenberg team uses in naming its APIs and draws understandable comparisons between how the legacy meta box and new Sidebar APIs work. Bonus points are awarded for explaining how to go about whitelisting use of the custom panel for one or more specific block types.