Hey Rivarrl ,
sorry for the delayed response! I didn't get around to check the TinyDB forum recently and didn't see this new thread.
Right now there's no direct way to do this in TinyDB besids using a custom test function like this:
db.search(where('tags').any(lambda doc: re.match('^app', doc)))
Feel free to open an issue on GitHub on this, maybe we can add a better API for this ?