This was basically triggered by this forum post: https://forum.backdropcms.org/forum/how-set-selected-tag-form-select-opt...
As it is currently, you cannot easily add attributes to individual options of select elements, and it requires either a lot of theming work, or to port a module like https://www.drupal.org/project/form_options_attributes. Even with that module, things are not consistent, so we should consider backporting the D8 solution being worked in https://www.drupal.org/node/342316
Recent comments
I am withdrawing my question for the following reason: https://forum.backdropcms.org/comment/8960#comment-8960
Error when trying to check for updates
My hosting is located in a country that blocks numerous online resources, so I am not surprised that updates and modules are unavailable. However, everything works perfectly on a local server...
Unable to run update - fails with Connection timed out
UPDATE: I fixed the errors that I found in the logs. They were related to deleting an old blog content type pulled over from Drupal that was still referenced in one of the layouts. I updated...
missing "add block" in custom layout