I would say Showcase is fine for this purpose; you should just make your post substantial: explain what’s going on and what the snippet can be used for. Basically, include enough information to make it useful for others. And of course add relevant tags, just like package showcases use the packages tag.
Another avenue could be writing a question and self-answering it. For example, Can I configure my document (e.g. draft/release version, color theme) when creating a PDF without modifying the Typst file directly? could be viewed as a vehicle for posting two useful snippets, just accompanied by explanations and useful hints.
Yet another way to get the snippets out would be contributing to the Typst Examples book.