I assume you are still working on Awk. There is no awk specific lexer in lexilla, so (unless you write one) you are stuck using a lexer that is "close enough". So the only reason to add a built-in type for awk would be to get the ctags symbol parser for awk. I'm not sure how up-to-date Hacking is about adding a parser, probably best to examine any recent PRs that do it.