Cyclomatic Complexity Violation: Function should have complexity 10 or less: currently complexity equals 13 (cyclomatic_complexity)

The method is too complex. But instead of rewriting the code, you could exclude switches from the cyclomatic_complexity calculation (since they are perfectly readable) like this:

cyclomatic_complexity:
  ignores_case_statements: true

The warning occurs because your function is too complex as defined by the metric which essentially counts the number of decisions that need to be made.

A simple way to avoid it in this particular case would be with some simple math:

func selectedMenuInLoggedOutState(sender: UIButton) {
    guard let menu = LeftGuestMenu(rawValue: sender.tag - 1) else { return }
    self.changeGuestViewController(menu)
}

You can disable swiftlint warnings in code like this:

// swiftlint:disable cyclomatic_complexity
func selectedMenuInLoggedOutState(sender: UIButton) {
    ...
}
// swiftlint:enable cyclomatic_complexity

or, if you want to explicitly just disable the next swiftlint warning:

// swiftlint:disable:next cyclomatic_complexity
func selectedMenuInLoggedOutState(sender: UIButton) {