This is not the first time people (including me) are asking where are the saves for W10 version of the game located.
Steam saves are located in "Saved Games -> Grounded" folder.
Windows 10 actually lets you export saves to "Saved Games -> Grounded Windows 10 Exported". But doesn't really seem to have a save location (or at least not an easily accessible one).
Many players are gonna be trying / tried the game on the free weekend and decided to progress further via the gamepass. So