I wrote the "ss one" User Guide https://ssnote.github.io/ss-one-ug/.
This app is simple. Draw something and export it as SVG.
An exported SVG file has 'ss one native format data' included. It can be importable SVG with 'ss one native format data' file. You can import this kind of file in this app again. (A pure SVG file does not support to import.)
See this entry ss one, introduction.
You can get this app on the google play store.