You can assign a property to a format to make the text of every instance of that format act as a related-topic keyword. Create a special @outputclass to use for this purpose.
For WinHelp, you can use either a character format or a paragraph format for related-topic keywords. For example, if an ALink keyword (“A” footnote) appears as a word in topic text, you can apply an inline element with a special @outputclass to the word, and in the configuration file assign property AKey to the resulting format:
[HelpStyles] ALinkCharFmt = AKey
Or, you can insert a block element containing only the keyword, add a special @outputclass, and also assign property Delete to the resulting format:
[HelpStyles] ALinkParaFmt = AKey Delete
See §17.10 Creating related-topic links in WinHelp.
For HTML-based Help you must use a block element (as opposed to an inline element) a for related-topic keywords. For example, you can put an ALink keyword in a block element by itself, add a special @outputclass, and in the configuration file assign property ALink to the resulting format (and property Delete, if you do not want the paragraph to appear in topic text):
[HtmlStyles] ; ALink, effective for MS HTML, OH, and Oracle Help, uses the contents ; of the para for the value of the ALink Name parameter of an ALink ; object. ALinkParaFmt = ALink Delete