The default download folder is determined by your browser setting.
E.g. in Google-Chrome: “Settings - Downloads - Ask where files should be stored”
You can download the maps to any directory you want.
You can also download the maps with your desktop PC, and copy them via USB onto the smartphone.
E.g. I have created a directory “kurviger-maps” on the SD card where I put all my maps.
PS:
I case you didn’t notice:
Kurviger 2.2.28 won’t work after your subscription has expired.