How do I add a new User Link under site avatar dropdown menu?


I am trying to add a new link and page under the avatar dropdown on the top righthand side, but I'm not sure how to do so.

I noticed you can enable/disable these user links in the configuration of the site banner, but I'm not sure how to edit their content pages or add new ones.

Guidance on where to do this and how much effort it would take are greatly appreciated! Note: I'm a functional consumer, so this will require custom code, that'd be great to point out.