It's a pretty cool builder. It's not very popular among Anno fans as it's a bit simpler compared to the rest of the franchise, but at the same time that makes it the best place to start if you're new to the franchise.
Took me 15 minutes to find as well. It's written in the RUNE.ini next to the executable: "Save data is stored at %SystemDrive%\Users\Public\Documents\uPlay\RUNE\Saves\Anno2205 "
"Save data is stored at %SystemDrive%\Users\Public\Documents\uPlay\RUNE\Saves\Anno2205 "
Have fun