WPTavern: A Gutenberg Migration Guide for Developers
In order to help developers learn how to migrate from the classic editor to Gutenberg, Daniel Bachhuber has launched a Gutenberg Migration Guide. Bachhuber is seeking the community’s help in identifying and filling a database to document all of the ways the classic editor can be customized.
Take a look through the Gutenberg Migration Guide. For each action, filter, and so on, we’d like to document real-world examples of how they’ve been used. Then, for each of those real-world examples, identify how the feature might be replicated in Gutenberg.
Daniel Bachhuber
He uses the media_buttons action as an example. This action is commonly used to add a button to the top of the editor. Developers can accomplish the same task in Gutenberg using the block inserter.
If you have any questions or suggestions, you’re encouraged to create a new issue on GitHub.
Source: WordPress