Humans are better at some things than others. We're really good, for example, at drawing a pretty picture of a flower, but we're not so good at instantly recalling the precise genus of that flower and its scientific name. Computers are better at that kind of thing.

The rule of thumb for the number of items that a person can reasonably remember and juggle in a list, is "seve, plus or minus two." (The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information, George A. Miller (1956) (https://www.ncbi.nlm.nih.gov/pubmed/13310704)). This research has been around since the 1950s and has been revised and re-evaluated many times over the years. I'll spare you the psychological study details, but the short version is: it's pretty much true.

The "magic number seven" will change depending on the items being recalled, the context, and environmental factors like state of mind, but it's as good a starting point as any. The point is: users can't manipulate and recall long lists of items in their minds.

If you're presenting a user with a list of options, keep in mind that by the time they've read the seventh or eighth option, they will likely have"filled the buffe" in their mind to capacity, and will struggle to remember what the first option was.

This also applies to menus, as well as sections and categories. All of these tasks are better served by other UI patterns described elsewhere in this book.

Try to group menus into sections, or reduce the complexity of options, so that the user doesn't have to struggle to recall them. Hide extra settings in "advanced" settings, for example. Your users are (probably) humans, not robots.