Note that since settings/configuration was never defined by the asker and no examples were given, I've written by answer using these definitions:
- settings, options available via the user interface, e.g the customizer, site editor, or settings pages.
- configuration, a larger scope that could include the above, but could also include
wp-config.php constants, PHP environment variables, nginx configs, and other PHP code or server/dev ops.
It is noted that the one example shared appears to be unrelated to both of them. It's also noted that these are not comprehensive dictionary definitions, it isn't my intention to provide a cast iron definition of the two.
Are Questions on Settings Adjustments in WordPress Core Allowed?
As long as they are programming/developer questions, as this is a stack for developers, not end users.
For example, what a constant defined in
wp-config.php does, or how to set the default value of a setting are ok. Those are programming questions.
Changing values in the browser in the default settings however is end user support which isn't appropriate for this stack. If it's something that can be answered by telling you to click buttons or fill in text boxes in the browser then that's in the realm of end user support and outside the stacks scope. E.g. changing the size of thumbnails in the media settings page, or the number of posts shown on archives on general settings.
Are Questions on Settings Adjustments in Third Party Themes and Plugins Allowed?
No. 3rd party plugin and theme dev support questions are offtopic and not in the scope of this stack. Contact their respected vendors support routes or ask in their associated communities.
Follow Up Notes
The presence of a plugin that answers does what you're asking in your question is irrelevant. You can ask how to do something, but you can't ask for a recommendation for a plugin that does it for you.
Take the opening of your question:
I'm trying to find out how to display a line number next to my hundreds of posts in the back end so I can clearly see where I left off.
This would be on topic and in scope, you're asking how to do it, someone could write an answer with some code and walk you through the steps.
Not sure if there is a plugin or if this would require coding.
This however, is off-topic. There's a difference between these:
- How do I implement ABC?
- Is there an ABC plugin?