Léonie Watson explains how the HTML tabindex attribute is used to manage keyboard focus. Of particular interest to me was a clarification of what
tabindex="-1" does (because I always forget).
When tabindex is set to a negative integer like -1, (the element) becomes programmatically focusable but it isn’t included in the tab order. In other words, it can’t be reached by someone using the tab key to navigate through content, but it can be focused on with scripting.