First of, I'm a huge fan of the new layout.
But as the title says I'd like to add my own beloved local files to the "Your Music". I don't see why this shouldn't be a possibilty. This way I don't need to have one master playlist, I can just have all the music I like under "Your Music -> Songs".
Also, as suggested earlier, changing the font size could be usable to many people.
Updated on 2018-08-28
Thanks for bringing us your feedback in the Spotify Idea Exchange.
We don't have plans to add Local Files to your music right now, so we're marking this as a 'Not Right Now'.
Rest assured we'll continue to check out the feedback here, and if there are any updates we'll let you know.