Wow, this is really an app that is absolutely great. You can say it's a must have app. You have already indicated that you want to add some playgrounds. So my suggestions will be the things you want to do anyway. But I will name them in spite of that. :D
These are the Playgrounds I would still like to see.
2D/3D Physics Playground.
Tween Playground
3D Particle Playground.
Maybe a Sound Playground.
Regarding the font size - yes, it is a bit small. I work with a 4K screen so everything seems very small. But I can manage.
The playgrounds orbit and wave ... - is nice to see how it works. But I don't know what to use it for.
The GUI is this also your OryUI? Or is it a different development?