To save, you open the quick menu by clicking the flower at the bottom right of the text box. It's also available for the PC version, you just have to hover on the flower.
I've added a tutorial on that, but it's not included in the demo version/s (the tutorial, that is).
The buttons are small though, and the android version is currently a direct port of the PC version, but I'll be making a more Android friendly UI after the full release (whenever that may be 😅)