Sorry for the delayed response. We are working on additional localization tools, though the next pass (early May probably) is going to focus on more loc support for Epic content first.
For community tutorials you can post content in Spanish alongside some other major languages. We are going for a system where each localized version of a tutorial is an entirely separate post, however in the future we will likely allow for posts to be added into a container so that Post A is aware that it is a translation of Post B and vice versa. For now please feel totally welcome to (re)post content with as a new post and set to Spanish, it should be compatible with the direction we are going!
Subtitles on Youtube videos are supported, if your video has multiple cc languages available it should show up and work.
For localizing and contributing to Epic content that one will not be possible yet. We are not sure yet where that is going to go direction wise.