After upgrading WordPress from v4.x to v5.x, you may find that the default editor for WordPress has changed. The old default editor is the “classic editor” and the new default editor is the “Gutenberg editor”, also known as the “block editor”. Because the content will be different types of blocks, such as Paragraph block, Gallery block, Image block, Heading block, and etc.
When you first edit a page or post in the new Gutenberg editor, you may find that the content created in the old default editor has been placed in a “Classic” block.
What’s the problem?
You can still edit these in the Classic block. However, there are some problems when editing the image library in the Classic block – new images cannot be saved when you want to replace or add images to the image library. We tested this operation in different themes and this problem always exists. Therefore, this should be a bug when converting content between these two editors.
How to resolve this problem?
In fact, it is easy to find a workaround for editing an image library.
Step 1 – Convert the content in the classic block into blocks.
Click anywhere in the Classic block and you will see the toolbar appear. Click the small icon in the upper right corner of the toolbar, and then click Convert to Blocks“.
You will see the content has been converted into different blocks: Paragraph, Heading, Quote, and so on. And the Slider Gallery (or the Justified Gallery) will be converted into a shortcode.
Step 2 – Add a new gallery block.
Please hover your cursor on the the block followed by the gallery shortcode, and then click on the “+” icon to add a new block before the highlighted block.
Then find “Theme Blocks” > “Slider Gallery”, or “Justified Gallery”, click on it to add the block into the page.
Please check our documentation to know more details about how to edit Theme Built-in Galleries: Slider & Justified Gallery.
Step 3 – Remove the old gallery shortcode.
And you will see the newly added Slider Gallery (or Justified Gallery) in the Gutenberg editor.
Some users may choose to still use the old editor. If you want to use the new Gutenberg editor, we recommend converting all the content created by the old editor (the classic blocks) into blocks in Gutenberg editor.