For anyone wanting to migrate their saves over, I figured out how to do it on windows.

Firstly the demo and full version save files are stored in the LocalLow folder in a folder named "Anneka Tran" (the developer). The address should look like "C:\Users\[your username]\AppData\LocalLow\Anneka Tran\Garden Galaxy Demo\Saves" or "C:\Users\[your username]\AppData\LocalLow\Anneka Tran\Garden Galaxy\Saves" for the full version.

(As always with save files, back them up to a separate folder before messing around with them!)

Secondly if you move saves from the demo folder you have to edit it with notepad and change the line that says ""saveVersionFull": false" to ""saveVersionFull": true" The text in the save files is not formatted so you will have to do ctrl+f to find the variable. I did also change the version in the save file to reflect the current version of the game but I don't know if that was necessary. If you find this is necessary it's the first line in the file, change it from ""version": "1.0.0"" to ""version": "1.0.10""

Once I did that I moved the save file into the full version save file folder. Make sure to rename the demo files with a number that does not conflict with your current full version save files (for instance in the demo version I had a save file called "save_01.sav" and in the full version I also had a save file called "save_01.sav" so I just renamed the demo file to "save_02.sav"). I have no idea what happens if you have more than 3 save files though....