Is it possible natively, or is there a plugin, that will use Coda's autocomplete function for user defined methods and variables?
Coda 2 has been released, and autocompleting user-defines functions is one of the new features.
There are several mailing list posts on coda-users from over the years discussing the missing dynamic auto-completion for Coda 1.
There appears to be no way to do this really dynamically, e.g. in the same source file.
If you have finished libraries you're just reusing, this might help you. It's about editing the language definition bundles' code completion property list files (e.g.