Instead of putting optional plurals in parentheses, use either plural or singular constructions and keep things consistent throughout your docset. Choose what is most appropriate for your docset and your audience. If it's important in a specific context to indicate both, use one or more.
Not recommended: To find your API key(s), visit the Credentials page.
Recommended: To find your API key, visit the Credentials page.
Not recommended: The value of the parent depends on the value(s) of its child(ren).
Recommended: The value of the parent depends on the values of its children.
Not recommended: You can use a physical linecard, which can contain port(s).
Recommended: You can use a physical linecard, which can contain one or more ports.