Example diversity: include a few hardcoded single-value or enum examples in filters

[bumblefudge]

Niels pointed out (just before a PR was merged and the comment disappeared) that we have many regexp patterns in the examples, in situations where a hard-coded value or an allowlist/enum would be more realistic. A non-normative (and thus not timeline-blocking) tweak would be to go in a swap out a regexp here and there so that people that read examples first see both kinds of filters represented?