The context menu only has the option to add a complete file type to git-lfs. It should be possible to add specific files, and specific folders, much like the context menu for gitignore works.
Example: In some cases, I really want to track some specific folders and files in LFS while others of the same filetype should live in regular git land. Specifically, the ".asset" extension in Unity is used for a ton of things ranging from simple, text-readable ScriptableObjects (which should live in git land) to texture arrays with a size of several hundred MB (that's for LFS then).
2nd Example: I might have files that are large, but need to be included in the repository. I want these (in a specific subfolder) to be in lfs storage, while files with the same extension in a different subfolder shouldn't be in lfs storage.