Config file question

I am fairly new to HA, been using it for about 2 months. I have several integrations installed and some HACS integrations. Every video I watch that explains how to do something, refers to modifying or adding code to the config.yaml. However, my config file only contains what I have manually added. Should installed integrations automatically add lines to the config.yaml file?

No
It’s only the lines you add that should be there

Well, many of those videos may be horribly outdated. Some things are doing in YAML, and some things in the UI. Anything you do in the UI (other than scripts or automations) writes to a “hidden” folder.

Once upon a time the devs tried having HA update configuration.yaml, but that came with side effects like re-ordering things, and stripping out all comments.