There is an "add block" button when users submit a new post. However, that button does not appear for the blogs we have imported over for Wordpress. How can we get this functionality to work for the imported blogs?
If those blog post is migrated from Wordpress, it will stored it as joomla editor wysiwyg by default, so those migrated blog post will not able to use "Add block" functionality.
If you would like to use Add block functionality, you have to start a new blog post from your site.
Unfortunately that was not possible to modify this from database, because each of the block have their own HTML structure, if you add some of the content in the block, it will store all the HTML code with the blog content in database.