How do I add classes to blocks? I am using Drupal 8 Panels and it is working fine. The problem currently I have is, that I want to add classes to individual blocks on the panel layout page. Is there a way to add classes to blocks on panel pages?something like the Drupal 7 version of CSS properties on panel panes?
For custom blocks it's pretty easy to add classes without any module. Simply add a text (plain) field - or whatever fit's your needs best, get the value in the block.html.twig (maybe use Twigs |clean_class filter) and add it to the classes.