This post by Jason Yingling look in detail the best practices for custom WordPress development when making new blocks in the WordPress editor and how to integrate these features into WordPress themes.
One interesting part of this tutorial focuses on where to put your new blocks, in your theme OR in a plugin:
The general rule of thumb for including functionality in plugins or themes is to keep themes to the presentation of content and use plugins for functionality.
Blocks fall under this same set of principles. And I fall into the camp that blocks should be included in plugins as they extend the functionality of WordPress.
Read the full thing here and make sure to have a WordPress support retainer in place with a specialist agency like Make Do to ensure you get the help and support you need when upgrading to the latest version of WordPress.
