Known Problems 

Row size too large 

Read this TYPO3 changelog document by @lolli for in depth explanation and more tips.

Field labels displayed as identifier 

In some areas in the TYPO3 backend fields created by Content Blocks are displayed with their identifier instead of the localized label. E.g. in the backend user permissions view or the list view / export view. The reason is that you can't define fields centrally in Content Blocks. Multiple Content Blocks can reuse the same field and define alternative labels. If you really need proper labels in these areas, we recommend to use TCA overrides in order to define a default label.

$GLOBALS['TCA']['tt_content']['columns']['my_prefix_my_identifier']['label'] = 'LLL:EXT:my_extension/path/to/locallang.xlf';

Missing asset symlink from extension 

If your extension does not contain a Resources/Public/ directory, the asset symlink under public/_assets/ will not be created. This issue most commonly occurs in deployment pipelines.

The reason is that Content Blocks generates its assets after Composer's autoloading step. When the Composer installer creates the asset symlinks, the extension's Resources/Public/ directory does not yet exist, so no symlink is created.