WordPress Gutenberg editor
WordPress 5 (deployed in February 2019) includes a complete redevelopment of the editor, named “Gutenberg”, which now features a new “block” system for working with media assets and complex markup.
Here is a Lynda course on WordPress 5 to help you get started with this new editor. Skip ahead to section 2, Content Management, as the introductory sections don’t apply to our environment. There is more information about the new features of WordPress 5 in the official announcement blog post.
Challenges and Workarounds
Because it is a new system, Gutenberg still is seeing growing pains and unanticipated challenges.
Workaround: Use a "Classic" block
If you prefer the old editor generally or just want to use it for a particular page, you can still do so in Gutenberg.
Jdd a single “Classic” block to a page/post and get the classic editor experience in the Gutenberg editor without having to add any additional blocks. The "Classic" block is listed under the "Formatting" category or you can search for it.